| /* |
| * Read-Copy Update mechanism for mutual exclusion |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| * |
| * Copyright IBM Corporation, 2008 |
| * |
| * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| * Manfred Spraul <manfred@colorfullife.com> |
| * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
| * |
| * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| * |
| * For detailed explanation of Read-Copy Update mechanism see - |
| * Documentation/RCU |
| */ |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/spinlock.h> |
| #include <linux/smp.h> |
| #include <linux/rcupdate.h> |
| #include <linux/interrupt.h> |
| #include <linux/sched.h> |
| #include <linux/nmi.h> |
| #include <linux/atomic.h> |
| #include <linux/bitops.h> |
| #include <linux/module.h> |
| #include <linux/completion.h> |
| #include <linux/moduleparam.h> |
| #include <linux/percpu.h> |
| #include <linux/notifier.h> |
| #include <linux/cpu.h> |
| #include <linux/mutex.h> |
| #include <linux/time.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/wait.h> |
| #include <linux/kthread.h> |
| #include <linux/prefetch.h> |
| |
| #include "rcutree.h" |
| |
| /* Data structures. */ |
| |
| static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
| |
| #define RCU_STATE_INITIALIZER(structname) { \ |
| .level = { &structname.node[0] }, \ |
| .levelcnt = { \ |
| NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
| NUM_RCU_LVL_1, \ |
| NUM_RCU_LVL_2, \ |
| NUM_RCU_LVL_3, \ |
| NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ |
| }, \ |
| .signaled = RCU_GP_IDLE, \ |
| .gpnum = -300, \ |
| .completed = -300, \ |
| .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ |
| .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ |
| .n_force_qs = 0, \ |
| .n_force_qs_ngp = 0, \ |
| .name = #structname, \ |
| } |
| |
| struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
| DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
| |
| struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
| DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
| |
| static struct rcu_state *rcu_state; |
| |
| int rcu_scheduler_active __read_mostly; |
| EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
| |
| /* |
| * Control variables for per-CPU and per-rcu_node kthreads. These |
| * handle all flavors of RCU. |
| */ |
| static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); |
| DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
| DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu); |
| DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
| DEFINE_PER_CPU(char, rcu_cpu_has_work); |
| static char rcu_kthreads_spawnable; |
| |
| static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
| static void invoke_rcu_cpu_kthread(void); |
| |
| #define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */ |
| |
| /* |
| * Track the rcutorture test sequence number and the update version |
| * number within a given test. The rcutorture_testseq is incremented |
| * on every rcutorture module load and unload, so has an odd value |
| * when a test is running. The rcutorture_vernum is set to zero |
| * when rcutorture starts and is incremented on each rcutorture update. |
| * These variables enable correlating rcutorture output with the |
| * RCU tracing information. |
| */ |
| unsigned long rcutorture_testseq; |
| unsigned long rcutorture_vernum; |
| |
| /* |
| * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
| * permit this function to be invoked without holding the root rcu_node |
| * structure's ->lock, but of course results can be subject to change. |
| */ |
| static int rcu_gp_in_progress(struct rcu_state *rsp) |
| { |
| return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
| } |
| |
| /* |
| * Note a quiescent state. Because we do not need to know |
| * how many quiescent states passed, just if there was at least |
| * one since the start of the grace period, this just sets a flag. |
| */ |
| void rcu_sched_qs(int cpu) |
| { |
| struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
| |
| rdp->passed_quiesc_completed = rdp->gpnum - 1; |
| barrier(); |
| rdp->passed_quiesc = 1; |
| } |
| |
| void rcu_bh_qs(int cpu) |
| { |
| struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
| |
| rdp->passed_quiesc_completed = rdp->gpnum - 1; |
| barrier(); |
| rdp->passed_quiesc = 1; |
| } |
| |
| /* |
| * Note a context switch. This is a quiescent state for RCU-sched, |
| * and requires special handling for preemptible RCU. |
| */ |
| void rcu_note_context_switch(int cpu) |
| { |
| rcu_sched_qs(cpu); |
| rcu_preempt_note_context_switch(cpu); |
| } |
| EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
| |
| #ifdef CONFIG_NO_HZ |
| DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
| .dynticks_nesting = 1, |
| .dynticks = ATOMIC_INIT(1), |
| }; |
| #endif /* #ifdef CONFIG_NO_HZ */ |
| |
| static int blimit = 10; /* Maximum callbacks per softirq. */ |
| static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
| static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
| |
| module_param(blimit, int, 0); |
| module_param(qhimark, int, 0); |
| module_param(qlowmark, int, 0); |
| |
| int rcu_cpu_stall_suppress __read_mostly; |
| module_param(rcu_cpu_stall_suppress, int, 0644); |
| |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
| static int rcu_pending(int cpu); |
| |
| /* |
| * Return the number of RCU-sched batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_sched(void) |
| { |
| return rcu_sched_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
| |
| /* |
| * Return the number of RCU BH batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_bh(void) |
| { |
| return rcu_bh_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| |
| /* |
| * Force a quiescent state for RCU BH. |
| */ |
| void rcu_bh_force_quiescent_state(void) |
| { |
| force_quiescent_state(&rcu_bh_state, 0); |
| } |
| EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); |
| |
| /* |
| * Record the number of times rcutorture tests have been initiated and |
| * terminated. This information allows the debugfs tracing stats to be |
| * correlated to the rcutorture messages, even when the rcutorture module |
| * is being repeatedly loaded and unloaded. In other words, we cannot |
| * store this state in rcutorture itself. |
| */ |
| void rcutorture_record_test_transition(void) |
| { |
| rcutorture_testseq++; |
| rcutorture_vernum = 0; |
| } |
| EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); |
| |
| /* |
| * Record the number of writer passes through the current rcutorture test. |
| * This is also used to correlate debugfs tracing stats with the rcutorture |
| * messages. |
| */ |
| void rcutorture_record_progress(unsigned long vernum) |
| { |
| rcutorture_vernum++; |
| } |
| EXPORT_SYMBOL_GPL(rcutorture_record_progress); |
| |
| /* |
| * Force a quiescent state for RCU-sched. |
| */ |
| void rcu_sched_force_quiescent_state(void) |
| { |
| force_quiescent_state(&rcu_sched_state, 0); |
| } |
| EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); |
| |
| /* |
| * Does the CPU have callbacks ready to be invoked? |
| */ |
| static int |
| cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
| { |
| return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
| } |
| |
| /* |
| * Does the current CPU require a yet-as-unscheduled grace period? |
| */ |
| static int |
| cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
| } |
| |
| /* |
| * Return the root node of the specified rcu_state structure. |
| */ |
| static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
| { |
| return &rsp->node[0]; |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * If the specified CPU is offline, tell the caller that it is in |
| * a quiescent state. Otherwise, whack it with a reschedule IPI. |
| * Grace periods can end up waiting on an offline CPU when that |
| * CPU is in the process of coming online -- it will be added to the |
| * rcu_node bitmasks before it actually makes it online. The same thing |
| * can happen while a CPU is in the process of coming online. Because this |
| * race is quite rare, we check for it after detecting that the grace |
| * period has been delayed rather than checking each and every CPU |
| * each and every time we start a new grace period. |
| */ |
| static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
| { |
| /* |
| * If the CPU is offline, it is in a quiescent state. We can |
| * trust its state not to change because interrupts are disabled. |
| */ |
| if (cpu_is_offline(rdp->cpu)) { |
| rdp->offline_fqs++; |
| return 1; |
| } |
| |
| /* If preemptible RCU, no point in sending reschedule IPI. */ |
| if (rdp->preemptible) |
| return 0; |
| |
| /* The CPU is online, so send it a reschedule IPI. */ |
| if (rdp->cpu != smp_processor_id()) |
| smp_send_reschedule(rdp->cpu); |
| else |
| set_need_resched(); |
| rdp->resched_ipi++; |
| return 0; |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #ifdef CONFIG_NO_HZ |
| |
| /** |
| * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
| * |
| * Enter nohz mode, in other words, -leave- the mode in which RCU |
| * read-side critical sections can occur. (Though RCU read-side |
| * critical sections can occur in irq handlers in nohz mode, a possibility |
| * handled by rcu_irq_enter() and rcu_irq_exit()). |
| */ |
| void rcu_enter_nohz(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| if (--rdtp->dynticks_nesting) { |
| local_irq_restore(flags); |
| return; |
| } |
| /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
| smp_mb__before_atomic_inc(); /* See above. */ |
| atomic_inc(&rdtp->dynticks); |
| smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ |
| WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
| local_irq_restore(flags); |
| |
| /* If the interrupt queued a callback, get out of dyntick mode. */ |
| if (in_irq() && |
| (__get_cpu_var(rcu_sched_data).nxtlist || |
| __get_cpu_var(rcu_bh_data).nxtlist || |
| rcu_preempt_needs_cpu(smp_processor_id()))) |
| set_need_resched(); |
| } |
| |
| /* |
| * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
| * |
| * Exit nohz mode, in other words, -enter- the mode in which RCU |
| * read-side critical sections normally occur. |
| */ |
| void rcu_exit_nohz(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| if (rdtp->dynticks_nesting++) { |
| local_irq_restore(flags); |
| return; |
| } |
| smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
| atomic_inc(&rdtp->dynticks); |
| /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ |
| smp_mb__after_atomic_inc(); /* See above. */ |
| WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
| local_irq_restore(flags); |
| } |
| |
| /** |
| * rcu_nmi_enter - inform RCU of entry to NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is active. |
| */ |
| void rcu_nmi_enter(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks_nmi_nesting == 0 && |
| (atomic_read(&rdtp->dynticks) & 0x1)) |
| return; |
| rdtp->dynticks_nmi_nesting++; |
| smp_mb__before_atomic_inc(); /* Force delay from prior write. */ |
| atomic_inc(&rdtp->dynticks); |
| /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ |
| smp_mb__after_atomic_inc(); /* See above. */ |
| WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
| } |
| |
| /** |
| * rcu_nmi_exit - inform RCU of exit from NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is no longer active. |
| */ |
| void rcu_nmi_exit(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks_nmi_nesting == 0 || |
| --rdtp->dynticks_nmi_nesting != 0) |
| return; |
| /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
| smp_mb__before_atomic_inc(); /* See above. */ |
| atomic_inc(&rdtp->dynticks); |
| smp_mb__after_atomic_inc(); /* Force delay to next write. */ |
| WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
| } |
| |
| /** |
| * rcu_irq_enter - inform RCU of entry to hard irq context |
| * |
| * If the CPU was idle with dynamic ticks active, this updates the |
| * rdtp->dynticks to let the RCU handling know that the CPU is active. |
| */ |
| void rcu_irq_enter(void) |
| { |
| rcu_exit_nohz(); |
| } |
| |
| /** |
| * rcu_irq_exit - inform RCU of exit from hard irq context |
| * |
| * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
| * to put let the RCU handling be aware that the CPU is going back to idle |
| * with no ticks. |
| */ |
| void rcu_irq_exit(void) |
| { |
| rcu_enter_nohz(); |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * Snapshot the specified CPU's dynticks counter so that we can later |
| * credit them with an implicit quiescent state. Return 1 if this CPU |
| * is in dynticks idle mode, which is an extended quiescent state. |
| */ |
| static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| { |
| rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
| return 0; |
| } |
| |
| /* |
| * Return true if the specified CPU has passed through a quiescent |
| * state by virtue of being in or having passed through an dynticks |
| * idle state since the last call to dyntick_save_progress_counter() |
| * for this same CPU. |
| */ |
| static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| { |
| unsigned long curr; |
| unsigned long snap; |
| |
| curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks); |
| snap = (unsigned long)rdp->dynticks_snap; |
| |
| /* |
| * If the CPU passed through or entered a dynticks idle phase with |
| * no active irq/NMI handlers, then we can safely pretend that the CPU |
| * already acknowledged the request to pass through a quiescent |
| * state. Either way, that CPU cannot possibly be in an RCU |
| * read-side critical section that started before the beginning |
| * of the current RCU grace period. |
| */ |
| if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) { |
| rdp->dynticks_fqs++; |
| return 1; |
| } |
| |
| /* Go check for the CPU being offline. */ |
| return rcu_implicit_offline_qs(rdp); |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #else /* #ifdef CONFIG_NO_HZ */ |
| |
| #ifdef CONFIG_SMP |
| |
| static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| { |
| return 0; |
| } |
| |
| static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| { |
| return rcu_implicit_offline_qs(rdp); |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #endif /* #else #ifdef CONFIG_NO_HZ */ |
| |
| int rcu_cpu_stall_suppress __read_mostly; |
| |
| static void record_gp_stall_check_time(struct rcu_state *rsp) |
| { |
| rsp->gp_start = jiffies; |
| rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
| } |
| |
| static void print_other_cpu_stall(struct rcu_state *rsp) |
| { |
| int cpu; |
| long delta; |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Only let one CPU complain about others per time interval. */ |
| |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| delta = jiffies - rsp->jiffies_stall; |
| if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| |
| /* |
| * Now rat on any tasks that got kicked up to the root rcu_node |
| * due to CPU offlining. |
| */ |
| rcu_print_task_stall(rnp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| /* |
| * OK, time to rat on our buddy... |
| * See Documentation/RCU/stallwarn.txt for info on how to debug |
| * RCU CPU stall warnings. |
| */ |
| printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {", |
| rsp->name); |
| rcu_for_each_leaf_node(rsp, rnp) { |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rcu_print_task_stall(rnp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| if (rnp->qsmask == 0) |
| continue; |
| for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
| if (rnp->qsmask & (1UL << cpu)) |
| printk(" %d", rnp->grplo + cpu); |
| } |
| printk("} (detected by %d, t=%ld jiffies)\n", |
| smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
| trigger_all_cpu_backtrace(); |
| |
| /* If so configured, complain about tasks blocking the grace period. */ |
| |
| rcu_print_detail_task_stall(rsp); |
| |
| force_quiescent_state(rsp, 0); /* Kick them all. */ |
| } |
| |
| static void print_cpu_stall(struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* |
| * OK, time to rat on ourselves... |
| * See Documentation/RCU/stallwarn.txt for info on how to debug |
| * RCU CPU stall warnings. |
| */ |
| printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n", |
| rsp->name, smp_processor_id(), jiffies - rsp->gp_start); |
| trigger_all_cpu_backtrace(); |
| |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
| rsp->jiffies_stall = |
| jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| set_need_resched(); /* kick ourselves to get things going. */ |
| } |
| |
| static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long j; |
| unsigned long js; |
| struct rcu_node *rnp; |
| |
| if (rcu_cpu_stall_suppress) |
| return; |
| j = ACCESS_ONCE(jiffies); |
| js = ACCESS_ONCE(rsp->jiffies_stall); |
| rnp = rdp->mynode; |
| if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { |
| |
| /* We haven't checked in, so go dump stack. */ |
| print_cpu_stall(rsp); |
| |
| } else if (rcu_gp_in_progress(rsp) && |
| ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { |
| |
| /* They had a few time units to dump stack, so complain. */ |
| print_other_cpu_stall(rsp); |
| } |
| } |
| |
| static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
| { |
| rcu_cpu_stall_suppress = 1; |
| return NOTIFY_DONE; |
| } |
| |
| /** |
| * rcu_cpu_stall_reset - prevent further stall warnings in current grace period |
| * |
| * Set the stall-warning timeout way off into the future, thus preventing |
| * any RCU CPU stall-warning messages from appearing in the current set of |
| * RCU grace periods. |
| * |
| * The caller must disable hard irqs. |
| */ |
| void rcu_cpu_stall_reset(void) |
| { |
| rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; |
| rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; |
| rcu_preempt_stall_reset(); |
| } |
| |
| static struct notifier_block rcu_panic_block = { |
| .notifier_call = rcu_panic, |
| }; |
| |
| static void __init check_cpu_stall_init(void) |
| { |
| atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); |
| } |
| |
| /* |
| * Update CPU-local rcu_data state to record the newly noticed grace period. |
| * This is used both when we started the grace period and when we notice |
| * that someone else started the grace period. The caller must hold the |
| * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
| * and must have irqs disabled. |
| */ |
| static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| if (rdp->gpnum != rnp->gpnum) { |
| /* |
| * If the current grace period is waiting for this CPU, |
| * set up to detect a quiescent state, otherwise don't |
| * go looking for one. |
| */ |
| rdp->gpnum = rnp->gpnum; |
| if (rnp->qsmask & rdp->grpmask) { |
| rdp->qs_pending = 1; |
| rdp->passed_quiesc = 0; |
| } else |
| rdp->qs_pending = 0; |
| } |
| } |
| |
| static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
| !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __note_new_gpnum(rsp, rnp, rdp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Did someone else start a new RCU grace period start since we last |
| * checked? Update local state appropriately if so. Must be called |
| * on the CPU corresponding to rdp. |
| */ |
| static int |
| check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| int ret = 0; |
| |
| local_irq_save(flags); |
| if (rdp->gpnum != rsp->gpnum) { |
| note_new_gpnum(rsp, rdp); |
| ret = 1; |
| } |
| local_irq_restore(flags); |
| return ret; |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. In addition, the corresponding leaf rcu_node structure's |
| * ->lock must be held by the caller, with irqs disabled. |
| */ |
| static void |
| __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Did another grace period end? */ |
| if (rdp->completed != rnp->completed) { |
| |
| /* Advance callbacks. No harm if list empty. */ |
| rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
| rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| /* Remember that we saw this grace-period completion. */ |
| rdp->completed = rnp->completed; |
| |
| /* |
| * If we were in an extended quiescent state, we may have |
| * missed some grace periods that others CPUs handled on |
| * our behalf. Catch up with this state to avoid noting |
| * spurious new grace periods. If another grace period |
| * has started, then rnp->gpnum will have advanced, so |
| * we will detect this later on. |
| */ |
| if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
| rdp->gpnum = rdp->completed; |
| |
| /* |
| * If RCU does not need a quiescent state from this CPU, |
| * then make sure that this CPU doesn't go looking for one. |
| */ |
| if ((rnp->qsmask & rdp->grpmask) == 0) |
| rdp->qs_pending = 0; |
| } |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. |
| */ |
| static void |
| rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
| !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Do per-CPU grace-period initialization for running CPU. The caller |
| * must hold the lock of the leaf rcu_node structure corresponding to |
| * this CPU. |
| */ |
| static void |
| rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Prior grace period ended, so advance callbacks for current CPU. */ |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| |
| /* |
| * Because this CPU just now started the new grace period, we know |
| * that all of its callbacks will be covered by this upcoming grace |
| * period, even the ones that were registered arbitrarily recently. |
| * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. |
| * |
| * Other CPUs cannot be sure exactly when the grace period started. |
| * Therefore, their recently registered callbacks must pass through |
| * an additional RCU_NEXT_READY stage, so that they will be handled |
| * by the next RCU grace period. |
| */ |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| /* Set state so that this CPU will detect the next quiescent state. */ |
| __note_new_gpnum(rsp, rnp, rdp); |
| } |
| |
| /* |
| * Start a new RCU grace period if warranted, re-initializing the hierarchy |
| * in preparation for detecting the next grace period. The caller must hold |
| * the root node's ->lock, which is released before return. Hard irqs must |
| * be disabled. |
| */ |
| static void |
| rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
| __releases(rcu_get_root(rsp)->lock) |
| { |
| struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
| if (cpu_needs_another_gp(rsp, rdp)) |
| rsp->fqs_need_gp = 1; |
| if (rnp->completed == rsp->completed) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| |
| /* |
| * Propagate new ->completed value to rcu_node structures |
| * so that other CPUs don't have to wait until the start |
| * of the next grace period to process their callbacks. |
| */ |
| rcu_for_each_node_breadth_first(rsp, rnp) { |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->completed = rsp->completed; |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| } |
| local_irq_restore(flags); |
| return; |
| } |
| |
| /* Advance to a new grace period and initialize state. */ |
| rsp->gpnum++; |
| WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
| rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
| rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| record_gp_stall_check_time(rsp); |
| |
| /* Special-case the common single-level case. */ |
| if (NUM_RCU_NODES == 1) { |
| rcu_preempt_check_blocked_tasks(rnp); |
| rnp->qsmask = rnp->qsmaskinit; |
| rnp->gpnum = rsp->gpnum; |
| rnp->completed = rsp->completed; |
| rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
| rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| rcu_preempt_boost_start_gp(rnp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| |
| raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
| |
| |
| /* Exclude any concurrent CPU-hotplug operations. */ |
| raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| |
| /* |
| * Set the quiescent-state-needed bits in all the rcu_node |
| * structures for all currently online CPUs in breadth-first |
| * order, starting from the root rcu_node structure. This |
| * operation relies on the layout of the hierarchy within the |
| * rsp->node[] array. Note that other CPUs will access only |
| * the leaves of the hierarchy, which still indicate that no |
| * grace period is in progress, at least until the corresponding |
| * leaf node has been initialized. In addition, we have excluded |
| * CPU-hotplug operations. |
| * |
| * Note that the grace period cannot complete until we finish |
| * the initialization process, as there will be at least one |
| * qsmask bit set in the root node until that time, namely the |
| * one corresponding to this CPU, due to the fact that we have |
| * irqs disabled. |
| */ |
| rcu_for_each_node_breadth_first(rsp, rnp) { |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rcu_preempt_check_blocked_tasks(rnp); |
| rnp->qsmask = rnp->qsmaskinit; |
| rnp->gpnum = rsp->gpnum; |
| rnp->completed = rsp->completed; |
| if (rnp == rdp->mynode) |
| rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| rcu_preempt_boost_start_gp(rnp); |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| } |
| |
| rnp = rcu_get_root(rsp); |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| } |
| |
| /* |
| * Report a full set of quiescent states to the specified rcu_state |
| * data structure. This involves cleaning up after the prior grace |
| * period and letting rcu_start_gp() start up the next grace period |
| * if one is needed. Note that the caller must hold rnp->lock, as |
| * required by rcu_start_gp(), which will release it. |
| */ |
| static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
| __releases(rcu_get_root(rsp)->lock) |
| { |
| unsigned long gp_duration; |
| |
| WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
| |
| /* |
| * Ensure that all grace-period and pre-grace-period activity |
| * is seen before the assignment to rsp->completed. |
| */ |
| smp_mb(); /* See above block comment. */ |
| gp_duration = jiffies - rsp->gp_start; |
| if (gp_duration > rsp->gp_max) |
| rsp->gp_max = gp_duration; |
| rsp->completed = rsp->gpnum; |
| rsp->signaled = RCU_GP_IDLE; |
| rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
| } |
| |
| /* |
| * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
| * Allows quiescent states for a group of CPUs to be reported at one go |
| * to the specified rcu_node structure, though all the CPUs in the group |
| * must be represented by the same rcu_node structure (which need not be |
| * a leaf rcu_node structure, though it often will be). That structure's |
| * lock must be held upon entry, and it is released before return. |
| */ |
| static void |
| rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
| struct rcu_node *rnp, unsigned long flags) |
| __releases(rnp->lock) |
| { |
| struct rcu_node *rnp_c; |
| |
| /* Walk up the rcu_node hierarchy. */ |
| for (;;) { |
| if (!(rnp->qsmask & mask)) { |
| |
| /* Our bit has already been cleared, so done. */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rnp->qsmask &= ~mask; |
| if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
| |
| /* Other bits still set at this level, so done. */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rnp->grpmask; |
| if (rnp->parent == NULL) { |
| |
| /* No more levels. Exit loop holding root lock. */ |
| |
| break; |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| rnp_c = rnp; |
| rnp = rnp->parent; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| WARN_ON_ONCE(rnp_c->qsmask); |
| } |
| |
| /* |
| * Get here if we are the last CPU to pass through a quiescent |
| * state for this grace period. Invoke rcu_report_qs_rsp() |
| * to clean up and start the next grace period if one is needed. |
| */ |
| rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
| } |
| |
| /* |
| * Record a quiescent state for the specified CPU to that CPU's rcu_data |
| * structure. This must be either called from the specified CPU, or |
| * called when the specified CPU is known to be offline (and when it is |
| * also known that no other CPU is concurrently trying to help the offline |
| * CPU). The lastcomp argument is used to make sure we are still in the |
| * grace period of interest. We don't want to end the current grace period |
| * based on quiescent states detected in an earlier grace period! |
| */ |
| static void |
| rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rnp = rdp->mynode; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (lastcomp != rnp->completed) { |
| |
| /* |
| * Someone beat us to it for this grace period, so leave. |
| * The race with GP start is resolved by the fact that we |
| * hold the leaf rcu_node lock, so that the per-CPU bits |
| * cannot yet be initialized -- so we would simply find our |
| * CPU's bit already cleared in rcu_report_qs_rnp() if this |
| * race occurred. |
| */ |
| rdp->passed_quiesc = 0; /* try again later! */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rdp->grpmask; |
| if ((rnp->qsmask & mask) == 0) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } else { |
| rdp->qs_pending = 0; |
| |
| /* |
| * This GP can't end until cpu checks in, so all of our |
| * callbacks can be processed during the next GP. |
| */ |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
| } |
| } |
| |
| /* |
| * Check to see if there is a new grace period of which this CPU |
| * is not yet aware, and if so, set up local rcu_data state for it. |
| * Otherwise, see if this CPU has just passed through its first |
| * quiescent state for this grace period, and record that fact if so. |
| */ |
| static void |
| rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| /* If there is now a new grace period, record and return. */ |
| if (check_for_new_grace_period(rsp, rdp)) |
| return; |
| |
| /* |
| * Does this CPU still need to do its part for current grace period? |
| * If no, return and let the other CPUs do their part as well. |
| */ |
| if (!rdp->qs_pending) |
| return; |
| |
| /* |
| * Was there a quiescent state since the beginning of the grace |
| * period? If no, then exit and wait for the next call. |
| */ |
| if (!rdp->passed_quiesc) |
| return; |
| |
| /* |
| * Tell RCU we are done (but rcu_report_qs_rdp() will be the |
| * judge of that). |
| */ |
| rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
| } |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| |
| /* |
| * Move a dying CPU's RCU callbacks to online CPU's callback list. |
| * Synchronization is not required because this function executes |
| * in stop_machine() context. |
| */ |
| static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
| { |
| int i; |
| /* current DYING CPU is cleared in the cpu_online_mask */ |
| int receive_cpu = cpumask_any(cpu_online_mask); |
| struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
| struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu); |
| |
| if (rdp->nxtlist == NULL) |
| return; /* irqs disabled, so comparison is stable. */ |
| |
| *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; |
| receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| receive_rdp->qlen += rdp->qlen; |
| receive_rdp->n_cbs_adopted += rdp->qlen; |
| rdp->n_cbs_orphaned += rdp->qlen; |
| |
| rdp->nxtlist = NULL; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| rdp->qlen = 0; |
| } |
| |
| /* |
| * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
| * and move all callbacks from the outgoing CPU to the current one. |
| * There can only be one CPU hotplug operation at a time, so no other |
| * CPU can be attempting to update rcu_cpu_kthread_task. |
| */ |
| static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| int need_report = 0; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp; |
| struct task_struct *t; |
| |
| /* Stop the CPU's kthread. */ |
| t = per_cpu(rcu_cpu_kthread_task, cpu); |
| if (t != NULL) { |
| per_cpu(rcu_cpu_kthread_task, cpu) = NULL; |
| kthread_stop(t); |
| } |
| |
| /* Exclude any attempts to start a new grace period. */ |
| raw_spin_lock_irqsave(&rsp->onofflock, flags); |
| |
| /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
| rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
| mask = rdp->grpmask; /* rnp->grplo is constant. */ |
| do { |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit &= ~mask; |
| if (rnp->qsmaskinit != 0) { |
| if (rnp != rdp->mynode) |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| break; |
| } |
| if (rnp == rdp->mynode) |
| need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
| else |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| mask = rnp->grpmask; |
| rnp = rnp->parent; |
| } while (rnp != NULL); |
| |
| /* |
| * We still hold the leaf rcu_node structure lock here, and |
| * irqs are still disabled. The reason for this subterfuge is |
| * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
| * held leads to deadlock. |
| */ |
| raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| rnp = rdp->mynode; |
| if (need_report & RCU_OFL_TASKS_NORM_GP) |
| rcu_report_unblock_qs_rnp(rnp, flags); |
| else |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| if (need_report & RCU_OFL_TASKS_EXP_GP) |
| rcu_report_exp_rnp(rsp, rnp); |
| rcu_node_kthread_setaffinity(rnp, -1); |
| } |
| |
| /* |
| * Remove the specified CPU from the RCU hierarchy and move any pending |
| * callbacks that it might have to the current CPU. This code assumes |
| * that at least one CPU in the system will remain running at all times. |
| * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
| */ |
| static void rcu_offline_cpu(int cpu) |
| { |
| __rcu_offline_cpu(cpu, &rcu_sched_state); |
| __rcu_offline_cpu(cpu, &rcu_bh_state); |
| rcu_preempt_offline_cpu(cpu); |
| } |
| |
| #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
| { |
| } |
| |
| static void rcu_offline_cpu(int cpu) |
| { |
| } |
| |
| #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| /* |
| * Invoke any RCU callbacks that have made it to the end of their grace |
| * period. Thottle as specified by rdp->blimit. |
| */ |
| static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_head *next, *list, **tail; |
| int count; |
| |
| /* If no callbacks are ready, just return.*/ |
| if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
| return; |
| |
| /* |
| * Extract the list of ready callbacks, disabling to prevent |
| * races with call_rcu() from interrupt handlers. |
| */ |
| local_irq_save(flags); |
| list = rdp->nxtlist; |
| rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
| *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| tail = rdp->nxttail[RCU_DONE_TAIL]; |
| for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
| if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
| rdp->nxttail[count] = &rdp->nxtlist; |
| local_irq_restore(flags); |
| |
| /* Invoke callbacks. */ |
| count = 0; |
| while (list) { |
| next = list->next; |
| prefetch(next); |
| debug_rcu_head_unqueue(list); |
| __rcu_reclaim(list); |
| list = next; |
| if (++count >= rdp->blimit) |
| break; |
| } |
| |
| local_irq_save(flags); |
| |
| /* Update count, and requeue any remaining callbacks. */ |
| rdp->qlen -= count; |
| rdp->n_cbs_invoked += count; |
| if (list != NULL) { |
| *tail = rdp->nxtlist; |
| rdp->nxtlist = list; |
| for (count = 0; count < RCU_NEXT_SIZE; count++) |
| if (&rdp->nxtlist == rdp->nxttail[count]) |
| rdp->nxttail[count] = tail; |
| else |
| break; |
| } |
| |
| /* Reinstate batch limit if we have worked down the excess. */ |
| if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
| rdp->blimit = blimit; |
| |
| /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
| if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| |
| local_irq_restore(flags); |
| |
| /* Re-raise the RCU softirq if there are callbacks remaining. */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| invoke_rcu_cpu_kthread(); |
| } |
| |
| /* |
| * Check to see if this CPU is in a non-context-switch quiescent state |
| * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
| * Also schedule the RCU softirq handler. |
| * |
| * This function must be called with hardirqs disabled. It is normally |
| * invoked from the scheduling-clock interrupt. If rcu_pending returns |
| * false, there is no point in invoking rcu_check_callbacks(). |
| */ |
| void rcu_check_callbacks(int cpu, int user) |
| { |
| if (user || |
| (idle_cpu(cpu) && rcu_scheduler_active && |
| !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
| |
| /* |
| * Get here if this CPU took its interrupt from user |
| * mode or from the idle loop, and if this is not a |
| * nested interrupt. In this case, the CPU is in |
| * a quiescent state, so note it. |
| * |
| * No memory barrier is required here because both |
| * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
| * variables that other CPUs neither access nor modify, |
| * at least not while the corresponding CPU is online. |
| */ |
| |
| rcu_sched_qs(cpu); |
| rcu_bh_qs(cpu); |
| |
| } else if (!in_softirq()) { |
| |
| /* |
| * Get here if this CPU did not take its interrupt from |
| * softirq, in other words, if it is not interrupting |
| * a rcu_bh read-side critical section. This is an _bh |
| * critical section, so note it. |
| */ |
| |
| rcu_bh_qs(cpu); |
| } |
| rcu_preempt_check_callbacks(cpu); |
| if (rcu_pending(cpu)) |
| invoke_rcu_cpu_kthread(); |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * Scan the leaf rcu_node structures, processing dyntick state for any that |
| * have not yet encountered a quiescent state, using the function specified. |
| * Also initiate boosting for any threads blocked on the root rcu_node. |
| * |
| * The caller must have suppressed start of new grace periods. |
| */ |
| static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
| { |
| unsigned long bit; |
| int cpu; |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rcu_for_each_leaf_node(rsp, rnp) { |
| mask = 0; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (!rcu_gp_in_progress(rsp)) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| if (rnp->qsmask == 0) { |
| rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
| continue; |
| } |
| cpu = rnp->grplo; |
| bit = 1; |
| for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
| if ((rnp->qsmask & bit) != 0 && |
| f(per_cpu_ptr(rsp->rda, cpu))) |
| mask |= bit; |
| } |
| if (mask != 0) { |
| |
| /* rcu_report_qs_rnp() releases rnp->lock. */ |
| rcu_report_qs_rnp(mask, rsp, rnp, flags); |
| continue; |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| rnp = rcu_get_root(rsp); |
| if (rnp->qsmask == 0) { |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ |
| } |
| } |
| |
| /* |
| * Force quiescent states on reluctant CPUs, and also detect which |
| * CPUs are in dyntick-idle mode. |
| */ |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| if (!rcu_gp_in_progress(rsp)) |
| return; /* No grace period in progress, nothing to force. */ |
| if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
| rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
| return; /* Someone else is already on the job. */ |
| } |
| if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
| goto unlock_fqs_ret; /* no emergency and done recently. */ |
| rsp->n_force_qs++; |
| raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| if(!rcu_gp_in_progress(rsp)) { |
| rsp->n_force_qs_ngp++; |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
| } |
| rsp->fqs_active = 1; |
| switch (rsp->signaled) { |
| case RCU_GP_IDLE: |
| case RCU_GP_INIT: |
| |
| break; /* grace period idle or initializing, ignore. */ |
| |
| case RCU_SAVE_DYNTICK: |
| if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
| break; /* So gcc recognizes the dead code. */ |
| |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| |
| /* Record dyntick-idle state. */ |
| force_qs_rnp(rsp, dyntick_save_progress_counter); |
| raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| if (rcu_gp_in_progress(rsp)) |
| rsp->signaled = RCU_FORCE_QS; |
| break; |
| |
| case RCU_FORCE_QS: |
| |
| /* Check dyntick-idle state, send IPI to laggarts. */ |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
| |
| /* Leave state in case more forcing is required. */ |
| |
| raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| break; |
| } |
| rsp->fqs_active = 0; |
| if (rsp->fqs_need_gp) { |
| raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
| rsp->fqs_need_gp = 0; |
| rcu_start_gp(rsp, flags); /* releases rnp->lock */ |
| return; |
| } |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| unlock_fqs_ret: |
| raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
| } |
| |
| #else /* #ifdef CONFIG_SMP */ |
| |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| { |
| set_need_resched(); |
| } |
| |
| #endif /* #else #ifdef CONFIG_SMP */ |
| |
| /* |
| * This does the RCU processing work from softirq context for the |
| * specified rcu_state and rcu_data structures. This may be called |
| * only from the CPU to whom the rdp belongs. |
| */ |
| static void |
| __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| |
| WARN_ON_ONCE(rdp->beenonline == 0); |
| |
| /* |
| * If an RCU GP has gone long enough, go check for dyntick |
| * idle CPUs and, if needed, send resched IPIs. |
| */ |
| if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
| force_quiescent_state(rsp, 1); |
| |
| /* |
| * Advance callbacks in response to end of earlier grace |
| * period that some other CPU ended. |
| */ |
| rcu_process_gp_end(rsp, rdp); |
| |
| /* Update RCU state based on any recent quiescent states. */ |
| rcu_check_quiescent_state(rsp, rdp); |
| |
| /* Does this CPU require a not-yet-started grace period? */ |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
| rcu_start_gp(rsp, flags); /* releases above lock */ |
| } |
| |
| /* If there are callbacks ready, invoke them. */ |
| rcu_do_batch(rsp, rdp); |
| } |
| |
| /* |
| * Do softirq processing for the current CPU. |
| */ |
| static void rcu_process_callbacks(void) |
| { |
| __rcu_process_callbacks(&rcu_sched_state, |
| &__get_cpu_var(rcu_sched_data)); |
| __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
| rcu_preempt_process_callbacks(); |
| |
| /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ |
| rcu_needs_cpu_flush(); |
| } |
| |
| /* |
| * Wake up the current CPU's kthread. This replaces raise_softirq() |
| * in earlier versions of RCU. Note that because we are running on |
| * the current CPU with interrupts disabled, the rcu_cpu_kthread_task |
| * cannot disappear out from under us. |
| */ |
| static void invoke_rcu_cpu_kthread(void) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| __this_cpu_write(rcu_cpu_has_work, 1); |
| if (__this_cpu_read(rcu_cpu_kthread_task) == NULL) { |
| local_irq_restore(flags); |
| return; |
| } |
| wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Wake up the specified per-rcu_node-structure kthread. |
| * Because the per-rcu_node kthreads are immortal, we don't need |
| * to do anything to keep them alive. |
| */ |
| static void invoke_rcu_node_kthread(struct rcu_node *rnp) |
| { |
| struct task_struct *t; |
| |
| t = rnp->node_kthread_task; |
| if (t != NULL) |
| wake_up_process(t); |
| } |
| |
| /* |
| * Set the specified CPU's kthread to run RT or not, as specified by |
| * the to_rt argument. The CPU-hotplug locks are held, so the task |
| * is not going away. |
| */ |
| static void rcu_cpu_kthread_setrt(int cpu, int to_rt) |
| { |
| int policy; |
| struct sched_param sp; |
| struct task_struct *t; |
| |
| t = per_cpu(rcu_cpu_kthread_task, cpu); |
| if (t == NULL) |
| return; |
| if (to_rt) { |
| policy = SCHED_FIFO; |
| sp.sched_priority = RCU_KTHREAD_PRIO; |
| } else { |
| policy = SCHED_NORMAL; |
| sp.sched_priority = 0; |
| } |
| sched_setscheduler_nocheck(t, policy, &sp); |
| } |
| |
| /* |
| * Timer handler to initiate the waking up of per-CPU kthreads that |
| * have yielded the CPU due to excess numbers of RCU callbacks. |
| * We wake up the per-rcu_node kthread, which in turn will wake up |
| * the booster kthread. |
| */ |
| static void rcu_cpu_kthread_timer(unsigned long arg) |
| { |
| struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg); |
| struct rcu_node *rnp = rdp->mynode; |
| |
| atomic_or(rdp->grpmask, &rnp->wakemask); |
| invoke_rcu_node_kthread(rnp); |
| } |
| |
| /* |
| * Drop to non-real-time priority and yield, but only after posting a |
| * timer that will cause us to regain our real-time priority if we |
| * remain preempted. Either way, we restore our real-time priority |
| * before returning. |
| */ |
| static void rcu_yield(void (*f)(unsigned long), unsigned long arg) |
| { |
| struct sched_param sp; |
| struct timer_list yield_timer; |
| |
| setup_timer_on_stack(&yield_timer, f, arg); |
| mod_timer(&yield_timer, jiffies + 2); |
| sp.sched_priority = 0; |
| sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); |
| set_user_nice(current, 19); |
| schedule(); |
| sp.sched_priority = RCU_KTHREAD_PRIO; |
| sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
| del_timer(&yield_timer); |
| } |
| |
| /* |
| * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU. |
| * This can happen while the corresponding CPU is either coming online |
| * or going offline. We cannot wait until the CPU is fully online |
| * before starting the kthread, because the various notifier functions |
| * can wait for RCU grace periods. So we park rcu_cpu_kthread() until |
| * the corresponding CPU is online. |
| * |
| * Return 1 if the kthread needs to stop, 0 otherwise. |
| * |
| * Caller must disable bh. This function can momentarily enable it. |
| */ |
| static int rcu_cpu_kthread_should_stop(int cpu) |
| { |
| while (cpu_is_offline(cpu) || |
| !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) || |
| smp_processor_id() != cpu) { |
| if (kthread_should_stop()) |
| return 1; |
| per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
| per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id(); |
| local_bh_enable(); |
| schedule_timeout_uninterruptible(1); |
| if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu))) |
| set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
| local_bh_disable(); |
| } |
| per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; |
| return 0; |
| } |
| |
| /* |
| * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
| * earlier RCU softirq. |
| */ |
| static int rcu_cpu_kthread(void *arg) |
| { |
| int cpu = (int)(long)arg; |
| unsigned long flags; |
| int spincnt = 0; |
| unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu); |
| char work; |
| char *workp = &per_cpu(rcu_cpu_has_work, cpu); |
| |
| for (;;) { |
| *statusp = RCU_KTHREAD_WAITING; |
| rcu_wait(*workp != 0 || kthread_should_stop()); |
| local_bh_disable(); |
| if (rcu_cpu_kthread_should_stop(cpu)) { |
| local_bh_enable(); |
| break; |
| } |
| *statusp = RCU_KTHREAD_RUNNING; |
| per_cpu(rcu_cpu_kthread_loops, cpu)++; |
| local_irq_save(flags); |
| work = *workp; |
| *workp = 0; |
| local_irq_restore(flags); |
| if (work) |
| rcu_process_callbacks(); |
| local_bh_enable(); |
| if (*workp != 0) |
| spincnt++; |
| else |
| spincnt = 0; |
| if (spincnt > 10) { |
| *statusp = RCU_KTHREAD_YIELDING; |
| rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); |
| spincnt = 0; |
| } |
| } |
| *statusp = RCU_KTHREAD_STOPPED; |
| return 0; |
| } |
| |
| /* |
| * Spawn a per-CPU kthread, setting up affinity and priority. |
| * Because the CPU hotplug lock is held, no other CPU will be attempting |
| * to manipulate rcu_cpu_kthread_task. There might be another CPU |
| * attempting to access it during boot, but the locking in kthread_bind() |
| * will enforce sufficient ordering. |
| */ |
| static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) |
| { |
| struct sched_param sp; |
| struct task_struct *t; |
| |
| if (!rcu_kthreads_spawnable || |
| per_cpu(rcu_cpu_kthread_task, cpu) != NULL) |
| return 0; |
| t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu); |
| if (IS_ERR(t)) |
| return PTR_ERR(t); |
| kthread_bind(t, cpu); |
| set_task_state(t, TASK_INTERRUPTIBLE); |
| per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; |
| WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); |
| per_cpu(rcu_cpu_kthread_task, cpu) = t; |
| sp.sched_priority = RCU_KTHREAD_PRIO; |
| sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| return 0; |
| } |
| |
| /* |
| * Per-rcu_node kthread, which is in charge of waking up the per-CPU |
| * kthreads when needed. We ignore requests to wake up kthreads |
| * for offline CPUs, which is OK because force_quiescent_state() |
| * takes care of this case. |
| */ |
| static int rcu_node_kthread(void *arg) |
| { |
| int cpu; |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp = (struct rcu_node *)arg; |
| struct sched_param sp; |
| struct task_struct *t; |
| |
| for (;;) { |
| rnp->node_kthread_status = RCU_KTHREAD_WAITING; |
| rcu_wait(atomic_read(&rnp->wakemask) != 0); |
| rnp->node_kthread_status = RCU_KTHREAD_RUNNING; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| mask = atomic_xchg(&rnp->wakemask, 0); |
| rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ |
| for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) { |
| if ((mask & 0x1) == 0) |
| continue; |
| preempt_disable(); |
| t = per_cpu(rcu_cpu_kthread_task, cpu); |
| if (!cpu_online(cpu) || t == NULL) { |
| preempt_enable(); |
| continue; |
| } |
| per_cpu(rcu_cpu_has_work, cpu) = 1; |
| sp.sched_priority = RCU_KTHREAD_PRIO; |
| sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| preempt_enable(); |
| } |
| } |
| /* NOTREACHED */ |
| rnp->node_kthread_status = RCU_KTHREAD_STOPPED; |
| return 0; |
| } |
| |
| /* |
| * Set the per-rcu_node kthread's affinity to cover all CPUs that are |
| * served by the rcu_node in question. The CPU hotplug lock is still |
| * held, so the value of rnp->qsmaskinit will be stable. |
| * |
| * We don't include outgoingcpu in the affinity set, use -1 if there is |
| * no outgoing CPU. If there are no CPUs left in the affinity set, |
| * this function allows the kthread to execute on any CPU. |
| */ |
| static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
| { |
| cpumask_var_t cm; |
| int cpu; |
| unsigned long mask = rnp->qsmaskinit; |
| |
| if (rnp->node_kthread_task == NULL) |
| return; |
| if (!alloc_cpumask_var(&cm, GFP_KERNEL)) |
| return; |
| cpumask_clear(cm); |
| for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
| if ((mask & 0x1) && cpu != outgoingcpu) |
| cpumask_set_cpu(cpu, cm); |
| if (cpumask_weight(cm) == 0) { |
| cpumask_setall(cm); |
| for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) |
| cpumask_clear_cpu(cpu, cm); |
| WARN_ON_ONCE(cpumask_weight(cm) == 0); |
| } |
| set_cpus_allowed_ptr(rnp->node_kthread_task, cm); |
| rcu_boost_kthread_setaffinity(rnp, cm); |
| free_cpumask_var(cm); |
| } |
| |
| /* |
| * Spawn a per-rcu_node kthread, setting priority and affinity. |
| * Called during boot before online/offline can happen, or, if |
| * during runtime, with the main CPU-hotplug locks held. So only |
| * one of these can be executing at a time. |
| */ |
| static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp, |
| struct rcu_node *rnp) |
| { |
| unsigned long flags; |
| int rnp_index = rnp - &rsp->node[0]; |
| struct sched_param sp; |
| struct task_struct *t; |
| |
| if (!rcu_kthreads_spawnable || |
| rnp->qsmaskinit == 0) |
| return 0; |
| if (rnp->node_kthread_task == NULL) { |
| t = kthread_create(rcu_node_kthread, (void *)rnp, |
| "rcun%d", rnp_index); |
| if (IS_ERR(t)) |
| return PTR_ERR(t); |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| set_task_state(t, TASK_INTERRUPTIBLE); |
| rnp->node_kthread_task = t; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| sp.sched_priority = 99; |
| sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| } |
| return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index); |
| } |
| |
| /* |
| * Spawn all kthreads -- called as soon as the scheduler is running. |
| */ |
| static int __init rcu_spawn_kthreads(void) |
| { |
| int cpu; |
| struct rcu_node *rnp; |
| |
| rcu_kthreads_spawnable = 1; |
| for_each_possible_cpu(cpu) { |
| per_cpu(rcu_cpu_has_work, cpu) = 0; |
| if (cpu_online(cpu)) |
| (void)rcu_spawn_one_cpu_kthread(cpu); |
| } |
| rnp = rcu_get_root(rcu_state); |
| (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| if (NUM_RCU_NODES > 1) { |
| rcu_for_each_leaf_node(rcu_state, rnp) |
| (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| } |
| return 0; |
| } |
| early_initcall(rcu_spawn_kthreads); |
| |
| static void |
| __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
| struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp; |
| |
| debug_rcu_head_queue(head); |
| head->func = func; |
| head->next = NULL; |
| |
| smp_mb(); /* Ensure RCU update seen before callback registry. */ |
| |
| /* |
| * Opportunistically note grace-period endings and beginnings. |
| * Note that we might see a beginning right after we see an |
| * end, but never vice versa, since this CPU has to pass through |
| * a quiescent state betweentimes. |
| */ |
| local_irq_save(flags); |
| rdp = this_cpu_ptr(rsp->rda); |
| |
| /* Add the callback to our list. */ |
| *rdp->nxttail[RCU_NEXT_TAIL] = head; |
| rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
| rdp->qlen++; |
| |
| /* If interrupts were disabled, don't dive into RCU core. */ |
| if (irqs_disabled_flags(flags)) { |
| local_irq_restore(flags); |
| return; |
| } |
| |
| /* |
| * Force the grace period if too many callbacks or too long waiting. |
| * Enforce hysteresis, and don't invoke force_quiescent_state() |
| * if some other CPU has recently done so. Also, don't bother |
| * invoking force_quiescent_state() if the newly enqueued callback |
| * is the only one waiting for a grace period to complete. |
| */ |
| if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
| |
| /* Are we ignoring a completed grace period? */ |
| rcu_process_gp_end(rsp, rdp); |
| check_for_new_grace_period(rsp, rdp); |
| |
| /* Start a new grace period if one not already started. */ |
| if (!rcu_gp_in_progress(rsp)) { |
| unsigned long nestflag; |
| struct rcu_node *rnp_root = rcu_get_root(rsp); |
| |
| raw_spin_lock_irqsave(&rnp_root->lock, nestflag); |
| rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ |
| } else { |
| /* Give the grace period a kick. */ |
| rdp->blimit = LONG_MAX; |
| if (rsp->n_force_qs == rdp->n_force_qs_snap && |
| *rdp->nxttail[RCU_DONE_TAIL] != head) |
| force_quiescent_state(rsp, 0); |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| } |
| } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
| force_quiescent_state(rsp, 1); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Queue an RCU-sched callback for invocation after a grace period. |
| */ |
| void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_sched_state); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_sched); |
| |
| /* |
| * Queue an RCU for invocation after a quicker grace period. |
| */ |
| void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_bh_state); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_bh); |
| |
| /** |
| * synchronize_sched - wait until an rcu-sched grace period has elapsed. |
| * |
| * Control will return to the caller some time after a full rcu-sched |
| * grace period has elapsed, in other words after all currently executing |
| * rcu-sched read-side critical sections have completed. These read-side |
| * critical sections are delimited by rcu_read_lock_sched() and |
| * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), |
| * local_irq_disable(), and so on may be used in place of |
| * rcu_read_lock_sched(). |
| * |
| * This means that all preempt_disable code sequences, including NMI and |
| * hardware-interrupt handlers, in progress on entry will have completed |
| * before this primitive returns. However, this does not guarantee that |
| * softirq handlers will have completed, since in some kernels, these |
| * handlers can run in process context, and can block. |
| * |
| * This primitive provides the guarantees made by the (now removed) |
| * synchronize_kernel() API. In contrast, synchronize_rcu() only |
| * guarantees that rcu_read_lock() sections will have completed. |
| * In "classic RCU", these two guarantees happen to be one and |
| * the same, but can differ in realtime RCU implementations. |
| */ |
| void synchronize_sched(void) |
| { |
| struct rcu_synchronize rcu; |
| |
| if (rcu_blocking_is_gp()) |
| return; |
| |
| init_rcu_head_on_stack(&rcu.head); |
| init_completion(&rcu.completion); |
| /* Will wake me after RCU finished. */ |
| call_rcu_sched(&rcu.head, wakeme_after_rcu); |
| /* Wait for it. */ |
| wait_for_completion(&rcu.completion); |
| destroy_rcu_head_on_stack(&rcu.head); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_sched); |
| |
| /** |
| * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. |
| * |
| * Control will return to the caller some time after a full rcu_bh grace |
| * period has elapsed, in other words after all currently executing rcu_bh |
| * read-side critical sections have completed. RCU read-side critical |
| * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), |
| * and may be nested. |
| */ |
| void synchronize_rcu_bh(void) |
| { |
| struct rcu_synchronize rcu; |
| |
| if (rcu_blocking_is_gp()) |
| return; |
| |
| init_rcu_head_on_stack(&rcu.head); |
| init_completion(&rcu.completion); |
| /* Will wake me after RCU finished. */ |
| call_rcu_bh(&rcu.head, wakeme_after_rcu); |
| /* Wait for it. */ |
| wait_for_completion(&rcu.completion); |
| destroy_rcu_head_on_stack(&rcu.head); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_rcu_bh); |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, for the specified type of RCU, returning 1 if so. |
| * The checks are in order of increasing expense: checks that can be |
| * carried out against CPU-local state are performed first. However, |
| * we must check for CPU stalls first, else we might not get a chance. |
| */ |
| static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| struct rcu_node *rnp = rdp->mynode; |
| |
| rdp->n_rcu_pending++; |
| |
| /* Check for CPU stalls, if enabled. */ |
| check_cpu_stall(rsp, rdp); |
| |
| /* Is the RCU core waiting for a quiescent state from this CPU? */ |
| if (rdp->qs_pending && !rdp->passed_quiesc) { |
| |
| /* |
| * If force_quiescent_state() coming soon and this CPU |
| * needs a quiescent state, and this is either RCU-sched |
| * or RCU-bh, force a local reschedule. |
| */ |
| rdp->n_rp_qs_pending++; |
| if (!rdp->preemptible && |
| ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, |
| jiffies)) |
| set_need_resched(); |
| } else if (rdp->qs_pending && rdp->passed_quiesc) { |
| rdp->n_rp_report_qs++; |
| return 1; |
| } |
| |
| /* Does this CPU have callbacks ready to invoke? */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
| rdp->n_rp_cb_ready++; |
| return 1; |
| } |
| |
| /* Has RCU gone idle with this CPU needing another grace period? */ |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| rdp->n_rp_cpu_needs_gp++; |
| return 1; |
| } |
| |
| /* Has another RCU grace period completed? */ |
| if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
| rdp->n_rp_gp_completed++; |
| return 1; |
| } |
| |
| /* Has a new RCU grace period started? */ |
| if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
| rdp->n_rp_gp_started++; |
| return 1; |
| } |
| |
| /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
| if (rcu_gp_in_progress(rsp) && |
| ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
| rdp->n_rp_need_fqs++; |
| return 1; |
| } |
| |
| /* nothing to do */ |
| rdp->n_rp_need_nothing++; |
| return 0; |
| } |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, returning 1 if so. This function is part of the |
| * RCU implementation; it is -not- an exported member of the RCU API. |
| */ |
| static int rcu_pending(int cpu) |
| { |
| return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
| __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
| rcu_preempt_pending(cpu); |
| } |
| |
| /* |
| * Check to see if any future RCU-related work will need to be done |
| * by the current CPU, even if none need be done immediately, returning |
| * 1 if so. |
| */ |
| static int rcu_needs_cpu_quick_check(int cpu) |
| { |
| /* RCU callbacks either ready or pending? */ |
| return per_cpu(rcu_sched_data, cpu).nxtlist || |
| per_cpu(rcu_bh_data, cpu).nxtlist || |
| rcu_preempt_needs_cpu(cpu); |
| } |
| |
| static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
| static atomic_t rcu_barrier_cpu_count; |
| static DEFINE_MUTEX(rcu_barrier_mutex); |
| static struct completion rcu_barrier_completion; |
| |
| static void rcu_barrier_callback(struct rcu_head *notused) |
| { |
| if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| complete(&rcu_barrier_completion); |
| } |
| |
| /* |
| * Called with preemption disabled, and from cross-cpu IRQ context. |
| */ |
| static void rcu_barrier_func(void *type) |
| { |
| int cpu = smp_processor_id(); |
| struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
| void (*call_rcu_func)(struct rcu_head *head, |
| void (*func)(struct rcu_head *head)); |
| |
| atomic_inc(&rcu_barrier_cpu_count); |
| call_rcu_func = type; |
| call_rcu_func(head, rcu_barrier_callback); |
| } |
| |
| /* |
| * Orchestrate the specified type of RCU barrier, waiting for all |
| * RCU callbacks of the specified type to complete. |
| */ |
| static void _rcu_barrier(struct rcu_state *rsp, |
| void (*call_rcu_func)(struct rcu_head *head, |
| void (*func)(struct rcu_head *head))) |
| { |
| BUG_ON(in_interrupt()); |
| /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
| mutex_lock(&rcu_barrier_mutex); |
| init_completion(&rcu_barrier_completion); |
| /* |
| * Initialize rcu_barrier_cpu_count to 1, then invoke |
| * rcu_barrier_func() on each CPU, so that each CPU also has |
| * incremented rcu_barrier_cpu_count. Only then is it safe to |
| * decrement rcu_barrier_cpu_count -- otherwise the first CPU |
| * might complete its grace period before all of the other CPUs |
| * did their increment, causing this function to return too |
| * early. Note that on_each_cpu() disables irqs, which prevents |
| * any CPUs from coming online or going offline until each online |
| * CPU has queued its RCU-barrier callback. |
| */ |
| atomic_set(&rcu_barrier_cpu_count, 1); |
| on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
| if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| complete(&rcu_barrier_completion); |
| wait_for_completion(&rcu_barrier_completion); |
| mutex_unlock(&rcu_barrier_mutex); |
| } |
| |
| /** |
| * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
| */ |
| void rcu_barrier_bh(void) |
| { |
| _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
| |
| /** |
| * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
| */ |
| void rcu_barrier_sched(void) |
| { |
| _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
| |
| /* |
| * Do boot-time initialization of a CPU's per-CPU RCU data. |
| */ |
| static void __init |
| rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| int i; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
| rdp->nxtlist = NULL; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| rdp->qlen = 0; |
| #ifdef CONFIG_NO_HZ |
| rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
| #endif /* #ifdef CONFIG_NO_HZ */ |
| rdp->cpu = cpu; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Initialize a CPU's per-CPU RCU data. Note that only one online or |
| * offline event can be happening at a given time. Note also that we |
| * can accept some slop in the rsp->completed access due to the fact |
| * that this CPU cannot possibly have any RCU callbacks in flight yet. |
| */ |
| static void __cpuinit |
| rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
| rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
| rdp->beenonline = 1; /* We have now been online. */ |
| rdp->preemptible = preemptible; |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->blimit = blimit; |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| |
| /* |
| * A new grace period might start here. If so, we won't be part |
| * of it, but that is OK, as we are currently in a quiescent state. |
| */ |
| |
| /* Exclude any attempts to start a new GP on large systems. */ |
| raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| |
| /* Add CPU to rcu_node bitmasks. */ |
| rnp = rdp->mynode; |
| mask = rdp->grpmask; |
| do { |
| /* Exclude any attempts to start a new GP on small systems. */ |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit |= mask; |
| mask = rnp->grpmask; |
| if (rnp == rdp->mynode) { |
| rdp->gpnum = rnp->completed; /* if GP in progress... */ |
| rdp->completed = rnp->completed; |
| rdp->passed_quiesc_completed = rnp->completed - 1; |
| } |
| raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| rnp = rnp->parent; |
| } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
| |
| raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| } |
| |
| static void __cpuinit rcu_online_cpu(int cpu) |
| { |
| rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
| rcu_init_percpu_data(cpu, &rcu_bh_state, 0); |
| rcu_preempt_init_percpu_data(cpu); |
| } |
| |
| static void __cpuinit rcu_online_kthreads(int cpu) |
| { |
| struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
| struct rcu_node *rnp = rdp->mynode; |
| |
| /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ |
| if (rcu_kthreads_spawnable) { |
| (void)rcu_spawn_one_cpu_kthread(cpu); |
| if (rnp->node_kthread_task == NULL) |
| (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| } |
| } |
| |
| /* |
| * Handle CPU online/offline notification events. |
| */ |
| static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| unsigned long action, void *hcpu) |
| { |
| long cpu = (long)hcpu; |
| struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
| struct rcu_node *rnp = rdp->mynode; |
| |
| switch (action) { |
| case CPU_UP_PREPARE: |
| case CPU_UP_PREPARE_FROZEN: |
| rcu_online_cpu(cpu); |
| rcu_online_kthreads(cpu); |
| break; |
| case CPU_ONLINE: |
| case CPU_DOWN_FAILED: |
| rcu_node_kthread_setaffinity(rnp, -1); |
| rcu_cpu_kthread_setrt(cpu, 1); |
| break; |
| case CPU_DOWN_PREPARE: |
| rcu_node_kthread_setaffinity(rnp, cpu); |
| rcu_cpu_kthread_setrt(cpu, 0); |
| break; |
| case CPU_DYING: |
| case CPU_DYING_FROZEN: |
| /* |
| * The whole machine is "stopped" except this CPU, so we can |
| * touch any data without introducing corruption. We send the |
| * dying CPU's callbacks to an arbitrarily chosen online CPU. |
| */ |
| rcu_send_cbs_to_online(&rcu_bh_state); |
| rcu_send_cbs_to_online(&rcu_sched_state); |
| rcu_preempt_send_cbs_to_online(); |
| break; |
| case CPU_DEAD: |
| case CPU_DEAD_FROZEN: |
| case CPU_UP_CANCELED: |
| case CPU_UP_CANCELED_FROZEN: |
| rcu_offline_cpu(cpu); |
| break; |
| default: |
| break; |
| } |
| return NOTIFY_OK; |
| } |
| |
| /* |
| * This function is invoked towards the end of the scheduler's initialization |
| * process. Before this is called, the idle task might contain |
| * RCU read-side critical sections (during which time, this idle |
| * task is booting the system). After this function is called, the |
| * idle tasks are prohibited from containing RCU read-side critical |
| * sections. This function also enables RCU lockdep checking. |
| */ |
| void rcu_scheduler_starting(void) |
| { |
| WARN_ON(num_online_cpus() != 1); |
| WARN_ON(nr_context_switches() > 0); |
| rcu_scheduler_active = 1; |
| } |
| |
| /* |
| * Compute the per-level fanout, either using the exact fanout specified |
| * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
| */ |
| #ifdef CONFIG_RCU_FANOUT_EXACT |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int i; |
| |
| for (i = NUM_RCU_LVLS - 1; i > 0; i--) |
| rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
| rsp->levelspread[0] = RCU_FANOUT_LEAF; |
| } |
| #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int ccur; |
| int cprv; |
| int i; |
| |
| cprv = NR_CPUS; |
| for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| ccur = rsp->levelcnt[i]; |
| rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
| cprv = ccur; |
| } |
| } |
| #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| |
| /* |
| * Helper function for rcu_init() that initializes one rcu_state structure. |
| */ |
| static void __init rcu_init_one(struct rcu_state *rsp, |
| struct rcu_data __percpu *rda) |
| { |
| static char *buf[] = { "rcu_node_level_0", |
| "rcu_node_level_1", |
| "rcu_node_level_2", |
| "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ |
| int cpustride = 1; |
| int i; |
| int j; |
| struct rcu_node *rnp; |
| |
| BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
| |
| /* Initialize the level-tracking arrays. */ |
| |
| for (i = 1; i < NUM_RCU_LVLS; i++) |
| rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
| rcu_init_levelspread(rsp); |
| |
| /* Initialize the elements themselves, starting from the leaves. */ |
| |
| for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| cpustride *= rsp->levelspread[i]; |
| rnp = rsp->level[i]; |
| for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
| raw_spin_lock_init(&rnp->lock); |
| lockdep_set_class_and_name(&rnp->lock, |
| &rcu_node_class[i], buf[i]); |
| rnp->gpnum = 0; |
| rnp->qsmask = 0; |
| rnp->qsmaskinit = 0; |
| rnp->grplo = j * cpustride; |
| rnp->grphi = (j + 1) * cpustride - 1; |
| if (rnp->grphi >= NR_CPUS) |
| rnp->grphi = NR_CPUS - 1; |
| if (i == 0) { |
| rnp->grpnum = 0; |
| rnp->grpmask = 0; |
| rnp->parent = NULL; |
| } else { |
| rnp->grpnum = j % rsp->levelspread[i - 1]; |
| rnp->grpmask = 1UL << rnp->grpnum; |
| rnp->parent = rsp->level[i - 1] + |
| j / rsp->levelspread[i - 1]; |
| } |
| rnp->level = i; |
| INIT_LIST_HEAD(&rnp->blkd_tasks); |
| } |
| } |
| |
| rsp->rda = rda; |
| rnp = rsp->level[NUM_RCU_LVLS - 1]; |
| for_each_possible_cpu(i) { |
| while (i > rnp->grphi) |
| rnp++; |
| per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
| rcu_boot_init_percpu_data(i, rsp); |
| } |
| } |
| |
| void __init rcu_init(void) |
| { |
| int cpu; |
| |
| rcu_bootup_announce(); |
| rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
| rcu_init_one(&rcu_bh_state, &rcu_bh_data); |
| __rcu_init_preempt(); |
| |
| /* |
| * We don't need protection against CPU-hotplug here because |
| * this is called early in boot, before either interrupts |
| * or the scheduler are operational. |
| */ |
| cpu_notifier(rcu_cpu_notify, 0); |
| for_each_online_cpu(cpu) |
| rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); |
| check_cpu_stall_init(); |
| } |
| |
| #include "rcutree_plugin.h" |