| /*- |
| * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org> |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of the author nor the names of any co-contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| /* |
| * Machine independent bits of reader/writer lock implementation. |
| */ |
| |
| #include <sys/bsd_cdefs.h> |
| //__FBSDID("$FreeBSD$"); |
| |
| //#include "opt_ddb.h" |
| //#include "opt_kdtrace.h" |
| //#include "opt_no_adaptive_rwlocks.h" |
| |
| #include <sys/bsd_param.h> |
| //#include <sys/ktr.h> |
| #include <sys/bsd_kernel.h> |
| #include <sys/bsd_lock.h> |
| #include <sys/bsd_mutex.h> |
| //#include <sys/proc.h> |
| #include <sys/bsd_rwlock.h> |
| //#include <sys/sysctl.h> |
| #include <sys/bsd_systm.h> |
| //#include <sys/turnstile.h> |
| |
| //#include <machine/cpu.h> |
| |
| #include "host_serv.h" |
| |
| //#define UPTCP_RWLOCK_DEBUG |
| #ifndef UPTCP_RWLOCK_DEBUG |
| #define UPTCP_RWLOCK_DEBUG_PRINT(fmt, args...) |
| #else |
| #define UPTCP_RWLOCK_DEBUG_PRINT(fmt, args...) \ |
| do{ \ |
| char str[256]; \ |
| sprintf(str, "[DAMON.RWLOCK]: %s", (fmt)); \ |
| printf(str, ## args); \ |
| }while(0); |
| #endif |
| |
| |
| #if defined(SMP) && !defined(NO_ADAPTIVE_RWLOCKS) |
| #define ADAPTIVE_RWLOCKS |
| #endif |
| |
| #ifdef ADAPTIVE_RWLOCKS |
| #define ROWNER_RETRIES 10 |
| #define ROWNER_LOOPS 10000 |
| #endif |
| |
| #ifdef DDB |
| #include <ddb/ddb.h> |
| |
| static void db_show_rwlock(struct lock_object *lock); |
| #endif |
| static void assert_rw(struct lock_object *lock, int what); |
| static void lock_rw(struct lock_object *lock, int how); |
| #ifdef KDTRACE_HOOKS |
| static int owner_rw(struct lock_object *lock, struct thread **owner); |
| #endif |
| static int unlock_rw(struct lock_object *lock); |
| |
| struct lock_class lock_class_rw = { |
| .lc_name = "rw", |
| .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_UPGRADABLE, |
| .lc_assert = assert_rw, |
| #ifdef DDB |
| .lc_ddb_show = db_show_rwlock, |
| #endif |
| .lc_lock = lock_rw, |
| .lc_unlock = unlock_rw, |
| #ifdef KDTRACE_HOOKS |
| .lc_owner = owner_rw, |
| #endif |
| }; |
| |
| /* |
| * Return a pointer to the owning thread if the lock is write-locked or |
| * NULL if the lock is unlocked or read-locked. |
| */ |
| #define rw_wowner(rw) \ |
| ((rw)->rw_lock & RW_LOCK_READ ? NULL : \ |
| (struct thread *)RW_OWNER((rw)->rw_lock)) |
| |
| /* |
| * Returns if a write owner is recursed. Write ownership is not assured |
| * here and should be previously checked. |
| */ |
| #define rw_recursed(rw) ((rw)->rw_recurse != 0) |
| |
| /* |
| * Return true if curthread helds the lock. |
| */ |
| #define rw_wlocked(rw) (rw_wowner((rw)) == curthread) |
| |
| /* |
| * Return a pointer to the owning thread for this lock who should receive |
| * any priority lent by threads that block on this lock. Currently this |
| * is identical to rw_wowner(). |
| */ |
| #define rw_owner(rw) rw_wowner(rw) |
| |
| #ifndef INVARIANTS |
| #define _rw_assert(rw, what, file, line) |
| #endif |
| |
| void |
| assert_rw(struct lock_object *lock, int what) |
| { |
| |
| rw_assert((struct rwlock *)lock, what); |
| } |
| |
| void |
| lock_rw(struct lock_object *lock, int how) |
| { |
| struct rwlock *rw; |
| |
| rw = (struct rwlock *)lock; |
| if (how) |
| rw_wlock(rw); |
| else |
| rw_rlock(rw); |
| } |
| |
| int |
| unlock_rw(struct lock_object *lock) |
| { |
| struct rwlock *rw; |
| |
| rw = (struct rwlock *)lock; |
| rw_assert(rw, RA_LOCKED | LA_NOTRECURSED); |
| if (rw->rw_lock & RW_LOCK_READ) { |
| rw_runlock(rw); |
| return (0); |
| } else { |
| rw_wunlock(rw); |
| return (1); |
| } |
| } |
| |
| #ifdef KDTRACE_HOOKS |
| int |
| owner_rw(struct lock_object *lock, struct thread **owner) |
| { |
| struct rwlock *rw = (struct rwlock *)lock; |
| uintptr_t x = rw->rw_lock; |
| |
| *owner = rw_wowner(rw); |
| return ((x & RW_LOCK_READ) != 0 ? (RW_READERS(x) != 0) : |
| (*owner != NULL)); |
| } |
| #endif |
| |
| void |
| rw_init_flags(struct rwlock *rw, const char *name, int opts) |
| { |
| int flags; |
| |
| MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET | |
| RW_RECURSE)) == 0); |
| ASSERT_ATOMIC_LOAD_PTR(rw->rw_lock, |
| ("%s: rw_lock not aligned for %s: %p", __func__, name, |
| &rw->rw_lock)); |
| |
| flags = LO_UPGRADABLE; |
| if (opts & RW_DUPOK) |
| flags |= LO_DUPOK; |
| if (opts & RW_NOPROFILE) |
| flags |= LO_NOPROFILE; |
| if (!(opts & RW_NOWITNESS)) |
| flags |= LO_WITNESS; |
| if (opts & RW_RECURSE) |
| flags |= LO_RECURSABLE; |
| if (opts & RW_QUIET) |
| flags |= LO_QUIET; |
| |
| rw->rw_lock = RW_UNLOCKED; |
| rw->rw_recurse = 0; |
| //lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags); |
| |
| rw->lock_object.lo_name = name; |
| rw->lock_object.lo_flags |= flags | LO_INITIALIZED; |
| rw->lock_object.lo_data = 0; |
| rw->lock_object.lo_owner = 0; |
| rw->lock_object.ext_lock = host_pthread_rwlock_init(); |
| |
| } |
| |
| void |
| rw_destroy(struct rwlock *rw) |
| { |
| |
| KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock not unlocked")); |
| KASSERT(rw->rw_recurse == 0, ("rw lock still recursed")); |
| rw->rw_lock = RW_DESTROYED; |
| //lock_destroy(&rw->lock_object); |
| |
| rw->lock_object.lo_flags &= ~LO_INITIALIZED; |
| host_pthread_rwlock_destory((void*)&rw->lock_object); |
| } |
| |
| void |
| rw_sysinit(void *arg) |
| { |
| struct rw_args *args = arg; |
| |
| rw_init(args->ra_rw, args->ra_desc); |
| } |
| |
| void |
| rw_sysinit_flags(void *arg) |
| { |
| struct rw_args_flags *args = arg; |
| |
| rw_init_flags(args->ra_rw, args->ra_desc, args->ra_flags); |
| } |
| |
| #if 0 |
| int |
| rw_wowned(struct rwlock *rw) |
| { |
| |
| return (rw_wowner(rw) == curthread); |
| } |
| |
| void |
| _rw_wlock(struct rwlock *rw, const char *file, int line) |
| { |
| |
| MPASS(curthread != NULL); |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_wlock() of destroyed rwlock @ %s:%d", file, line)); |
| WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, |
| line, NULL); |
| __rw_wlock(rw, curthread, file, line); |
| LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); |
| WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); |
| curthread->td_locks++; |
| } |
| |
| int |
| _rw_try_wlock(struct rwlock *rw, const char *file, int line) |
| { |
| int rval; |
| |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_try_wlock() of destroyed rwlock @ %s:%d", file, line)); |
| |
| if (rw_wlocked(rw) && |
| (rw->lock_object.lo_flags & LO_RECURSABLE) != 0) { |
| rw->rw_recurse++; |
| rval = 1; |
| } else |
| rval = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_UNLOCKED, |
| (uintptr_t)curthread); |
| |
| LOCK_LOG_TRY("WLOCK", &rw->lock_object, 0, rval, file, line); |
| if (rval) { |
| WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, |
| file, line); |
| curthread->td_locks++; |
| } |
| return (rval); |
| } |
| |
| void |
| _rw_wunlock(struct rwlock *rw, const char *file, int line) |
| { |
| |
| MPASS(curthread != NULL); |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_wunlock() of destroyed rwlock @ %s:%d", file, line)); |
| _rw_assert(rw, RA_WLOCKED, file, line); |
| curthread->td_locks--; |
| WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); |
| LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file, |
| line); |
| if (!rw_recursed(rw)) |
| LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_WUNLOCK_RELEASE, rw); |
| __rw_wunlock(rw, curthread, file, line); |
| } |
| /* |
| * Determines whether a new reader can acquire a lock. Succeeds if the |
| * reader already owns a read lock and the lock is locked for read to |
| * prevent deadlock from reader recursion. Also succeeds if the lock |
| * is unlocked and has no writer waiters or spinners. Failing otherwise |
| * prioritizes writers before readers. |
| */ |
| #define RW_CAN_READ(_rw) \ |
| ((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \ |
| (RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \ |
| RW_LOCK_READ) |
| |
| void |
| _rw_rlock(struct rwlock *rw, const char *file, int line) |
| { |
| struct turnstile *ts; |
| #ifdef ADAPTIVE_RWLOCKS |
| volatile struct thread *owner; |
| int spintries = 0; |
| int i; |
| #endif |
| #ifdef LOCK_PROFILING |
| uint64_t waittime = 0; |
| int contested = 0; |
| #endif |
| uintptr_t v; |
| #ifdef KDTRACE_HOOKS |
| uint64_t spin_cnt = 0; |
| uint64_t sleep_cnt = 0; |
| int64_t sleep_time = 0; |
| #endif |
| |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); |
| KASSERT(rw_wowner(rw) != curthread, |
| ("%s (%s): wlock already held @ %s:%d", __func__, |
| rw->lock_object.lo_name, file, line)); |
| WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); |
| |
| for (;;) { |
| #ifdef KDTRACE_HOOKS |
| spin_cnt++; |
| #endif |
| /* |
| * Handle the easy case. If no other thread has a write |
| * lock, then try to bump up the count of read locks. Note |
| * that we have to preserve the current state of the |
| * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a |
| * read lock, then rw_lock must have changed, so restart |
| * the loop. Note that this handles the case of a |
| * completely unlocked rwlock since such a lock is encoded |
| * as a read lock with no waiters. |
| */ |
| v = rw->rw_lock; |
| if (RW_CAN_READ(v)) { |
| /* |
| * The RW_LOCK_READ_WAITERS flag should only be set |
| * if the lock has been unlocked and write waiters |
| * were present. |
| */ |
| if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, |
| v + RW_ONE_READER)) { |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR4(KTR_LOCK, |
| "%s: %p succeed %p -> %p", __func__, |
| rw, (void *)v, |
| (void *)(v + RW_ONE_READER)); |
| break; |
| } |
| continue; |
| } |
| lock_profile_obtain_lock_failed(&rw->lock_object, |
| &contested, &waittime); |
| |
| #ifdef ADAPTIVE_RWLOCKS |
| /* |
| * If the owner is running on another CPU, spin until |
| * the owner stops running or the state of the lock |
| * changes. |
| */ |
| if ((v & RW_LOCK_READ) == 0) { |
| owner = (struct thread *)RW_OWNER(v); |
| if (TD_IS_RUNNING(owner)) { |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR3(KTR_LOCK, |
| "%s: spinning on %p held by %p", |
| __func__, rw, owner); |
| while ((struct thread*)RW_OWNER(rw->rw_lock) == |
| owner && TD_IS_RUNNING(owner)) { |
| cpu_spinwait(); |
| #ifdef KDTRACE_HOOKS |
| spin_cnt++; |
| #endif |
| } |
| continue; |
| } |
| } else if (spintries < ROWNER_RETRIES) { |
| spintries++; |
| for (i = 0; i < ROWNER_LOOPS; i++) { |
| v = rw->rw_lock; |
| if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) |
| break; |
| cpu_spinwait(); |
| } |
| if (i != ROWNER_LOOPS) |
| continue; |
| } |
| #endif |
| |
| /* |
| * Okay, now it's the hard case. Some other thread already |
| * has a write lock or there are write waiters present, |
| * acquire the turnstile lock so we can begin the process |
| * of blocking. |
| */ |
| ts = turnstile_trywait(&rw->lock_object); |
| |
| /* |
| * The lock might have been released while we spun, so |
| * recheck its state and restart the loop if needed. |
| */ |
| v = rw->rw_lock; |
| if (RW_CAN_READ(v)) { |
| turnstile_cancel(ts); |
| continue; |
| } |
| |
| #ifdef ADAPTIVE_RWLOCKS |
| /* |
| * The current lock owner might have started executing |
| * on another CPU (or the lock could have changed |
| * owners) while we were waiting on the turnstile |
| * chain lock. If so, drop the turnstile lock and try |
| * again. |
| */ |
| if ((v & RW_LOCK_READ) == 0) { |
| owner = (struct thread *)RW_OWNER(v); |
| if (TD_IS_RUNNING(owner)) { |
| turnstile_cancel(ts); |
| continue; |
| } |
| } |
| #endif |
| |
| /* |
| * The lock is held in write mode or it already has waiters. |
| */ |
| MPASS(!RW_CAN_READ(v)); |
| |
| /* |
| * If the RW_LOCK_READ_WAITERS flag is already set, then |
| * we can go ahead and block. If it is not set then try |
| * to set it. If we fail to set it drop the turnstile |
| * lock and restart the loop. |
| */ |
| if (!(v & RW_LOCK_READ_WAITERS)) { |
| if (!atomic_cmpset_ptr(&rw->rw_lock, v, |
| v | RW_LOCK_READ_WAITERS)) { |
| turnstile_cancel(ts); |
| continue; |
| } |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p set read waiters flag", |
| __func__, rw); |
| } |
| |
| /* |
| * We were unable to acquire the lock and the read waiters |
| * flag is set, so we must block on the turnstile. |
| */ |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, |
| rw); |
| #ifdef KDTRACE_HOOKS |
| sleep_time -= lockstat_nsecs(); |
| #endif |
| turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); |
| #ifdef KDTRACE_HOOKS |
| sleep_time += lockstat_nsecs(); |
| sleep_cnt++; |
| #endif |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p resuming from turnstile", |
| __func__, rw); |
| } |
| |
| /* |
| * TODO: acquire "owner of record" here. Here be turnstile dragons |
| * however. turnstiles don't like owners changing between calls to |
| * turnstile_wait() currently. |
| */ |
| LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_RLOCK_ACQUIRE, rw, contested, |
| waittime, file, line); |
| LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); |
| WITNESS_LOCK(&rw->lock_object, 0, file, line); |
| curthread->td_locks++; |
| curthread->td_rw_rlocks++; |
| #ifdef KDTRACE_HOOKS |
| if (sleep_time) |
| LOCKSTAT_RECORD1(LS_RW_RLOCK_BLOCK, rw, sleep_time); |
| |
| /* |
| * Record only the loops spinning and not sleeping. |
| */ |
| if (spin_cnt > sleep_cnt) |
| LOCKSTAT_RECORD1(LS_RW_RLOCK_SPIN, rw, (spin_cnt - sleep_cnt)); |
| #endif |
| } |
| |
| int |
| _rw_try_rlock(struct rwlock *rw, const char *file, int line) |
| { |
| uintptr_t x; |
| |
| for (;;) { |
| x = rw->rw_lock; |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line)); |
| if (!(x & RW_LOCK_READ)) |
| break; |
| if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) { |
| LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file, |
| line); |
| WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line); |
| curthread->td_locks++; |
| curthread->td_rw_rlocks++; |
| return (1); |
| } |
| } |
| |
| LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line); |
| return (0); |
| } |
| |
| void |
| _rw_runlock(struct rwlock *rw, const char *file, int line) |
| { |
| struct turnstile *ts; |
| uintptr_t x, v, queue; |
| |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); |
| _rw_assert(rw, RA_RLOCKED, file, line); |
| curthread->td_locks--; |
| curthread->td_rw_rlocks--; |
| WITNESS_UNLOCK(&rw->lock_object, 0, file, line); |
| LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); |
| |
| /* TODO: drop "owner of record" here. */ |
| |
| for (;;) { |
| /* |
| * See if there is more than one read lock held. If so, |
| * just drop one and return. |
| */ |
| x = rw->rw_lock; |
| if (RW_READERS(x) > 1) { |
| if (atomic_cmpset_rel_ptr(&rw->rw_lock, x, |
| x - RW_ONE_READER)) { |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR4(KTR_LOCK, |
| "%s: %p succeeded %p -> %p", |
| __func__, rw, (void *)x, |
| (void *)(x - RW_ONE_READER)); |
| break; |
| } |
| continue; |
| } |
| /* |
| * If there aren't any waiters for a write lock, then try |
| * to drop it quickly. |
| */ |
| if (!(x & RW_LOCK_WAITERS)) { |
| MPASS((x & ~RW_LOCK_WRITE_SPINNER) == |
| RW_READERS_LOCK(1)); |
| if (atomic_cmpset_rel_ptr(&rw->rw_lock, x, |
| RW_UNLOCKED)) { |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p last succeeded", |
| __func__, rw); |
| break; |
| } |
| continue; |
| } |
| /* |
| * Ok, we know we have waiters and we think we are the |
| * last reader, so grab the turnstile lock. |
| */ |
| turnstile_chain_lock(&rw->lock_object); |
| v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); |
| MPASS(v & RW_LOCK_WAITERS); |
| |
| /* |
| * Try to drop our lock leaving the lock in a unlocked |
| * state. |
| * |
| * If you wanted to do explicit lock handoff you'd have to |
| * do it here. You'd also want to use turnstile_signal() |
| * and you'd have to handle the race where a higher |
| * priority thread blocks on the write lock before the |
| * thread you wakeup actually runs and have the new thread |
| * "steal" the lock. For now it's a lot simpler to just |
| * wakeup all of the waiters. |
| * |
| * As above, if we fail, then another thread might have |
| * acquired a read lock, so drop the turnstile lock and |
| * restart. |
| */ |
| x = RW_UNLOCKED; |
| if (v & RW_LOCK_WRITE_WAITERS) { |
| queue = TS_EXCLUSIVE_QUEUE; |
| x |= (v & RW_LOCK_READ_WAITERS); |
| } else |
| queue = TS_SHARED_QUEUE; |
| if (!atomic_cmpset_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, |
| x)) { |
| turnstile_chain_unlock(&rw->lock_object); |
| continue; |
| } |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", |
| __func__, rw); |
| |
| /* |
| * Ok. The lock is released and all that's left is to |
| * wake up the waiters. Note that the lock might not be |
| * free anymore, but in that case the writers will just |
| * block again if they run before the new lock holder(s) |
| * release the lock. |
| */ |
| ts = turnstile_lookup(&rw->lock_object); |
| MPASS(ts != NULL); |
| turnstile_broadcast(ts, queue); |
| turnstile_unpend(ts, TS_SHARED_LOCK); |
| turnstile_chain_unlock(&rw->lock_object); |
| break; |
| } |
| LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_RUNLOCK_RELEASE, rw); |
| } |
| |
| /* |
| * This function is called when we are unable to obtain a write lock on the |
| * first try. This means that at least one other thread holds either a |
| * read or write lock. |
| */ |
| void |
| _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) |
| { |
| struct turnstile *ts; |
| #ifdef ADAPTIVE_RWLOCKS |
| volatile struct thread *owner; |
| int spintries = 0; |
| int i; |
| #endif |
| uintptr_t v, x; |
| #ifdef LOCK_PROFILING |
| uint64_t waittime = 0; |
| int contested = 0; |
| #endif |
| #ifdef KDTRACE_HOOKS |
| uint64_t spin_cnt = 0; |
| uint64_t sleep_cnt = 0; |
| int64_t sleep_time = 0; |
| #endif |
| |
| if (rw_wlocked(rw)) { |
| KASSERT(rw->lock_object.lo_flags & LO_RECURSABLE, |
| ("%s: recursing but non-recursive rw %s @ %s:%d\n", |
| __func__, rw->lock_object.lo_name, file, line)); |
| rw->rw_recurse++; |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); |
| return; |
| } |
| |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, |
| rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); |
| |
| while (!_rw_write_lock(rw, tid)) { |
| #ifdef KDTRACE_HOOKS |
| spin_cnt++; |
| #endif |
| lock_profile_obtain_lock_failed(&rw->lock_object, |
| &contested, &waittime); |
| #ifdef ADAPTIVE_RWLOCKS |
| /* |
| * If the lock is write locked and the owner is |
| * running on another CPU, spin until the owner stops |
| * running or the state of the lock changes. |
| */ |
| v = rw->rw_lock; |
| owner = (struct thread *)RW_OWNER(v); |
| if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR3(KTR_LOCK, "%s: spinning on %p held by %p", |
| __func__, rw, owner); |
| while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && |
| TD_IS_RUNNING(owner)) { |
| cpu_spinwait(); |
| #ifdef KDTRACE_HOOKS |
| spin_cnt++; |
| #endif |
| } |
| continue; |
| } |
| if ((v & RW_LOCK_READ) && RW_READERS(v) && |
| spintries < ROWNER_RETRIES) { |
| if (!(v & RW_LOCK_WRITE_SPINNER)) { |
| if (!atomic_cmpset_ptr(&rw->rw_lock, v, |
| v | RW_LOCK_WRITE_SPINNER)) { |
| continue; |
| } |
| } |
| spintries++; |
| for (i = 0; i < ROWNER_LOOPS; i++) { |
| if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) |
| break; |
| cpu_spinwait(); |
| } |
| #ifdef KDTRACE_HOOKS |
| spin_cnt += ROWNER_LOOPS - i; |
| #endif |
| if (i != ROWNER_LOOPS) |
| continue; |
| } |
| #endif |
| ts = turnstile_trywait(&rw->lock_object); |
| v = rw->rw_lock; |
| |
| #ifdef ADAPTIVE_RWLOCKS |
| /* |
| * The current lock owner might have started executing |
| * on another CPU (or the lock could have changed |
| * owners) while we were waiting on the turnstile |
| * chain lock. If so, drop the turnstile lock and try |
| * again. |
| */ |
| if (!(v & RW_LOCK_READ)) { |
| owner = (struct thread *)RW_OWNER(v); |
| if (TD_IS_RUNNING(owner)) { |
| turnstile_cancel(ts); |
| continue; |
| } |
| } |
| #endif |
| /* |
| * Check for the waiters flags about this rwlock. |
| * If the lock was released, without maintain any pending |
| * waiters queue, simply try to acquire it. |
| * If a pending waiters queue is present, claim the lock |
| * ownership and maintain the pending queue. |
| */ |
| x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); |
| if ((v & ~x) == RW_UNLOCKED) { |
| x &= ~RW_LOCK_WRITE_SPINNER; |
| if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) { |
| if (x) |
| turnstile_claim(ts); |
| else |
| turnstile_cancel(ts); |
| break; |
| } |
| turnstile_cancel(ts); |
| continue; |
| } |
| /* |
| * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to |
| * set it. If we fail to set it, then loop back and try |
| * again. |
| */ |
| if (!(v & RW_LOCK_WRITE_WAITERS)) { |
| if (!atomic_cmpset_ptr(&rw->rw_lock, v, |
| v | RW_LOCK_WRITE_WAITERS)) { |
| turnstile_cancel(ts); |
| continue; |
| } |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p set write waiters flag", |
| __func__, rw); |
| } |
| /* |
| * We were unable to acquire the lock and the write waiters |
| * flag is set, so we must block on the turnstile. |
| */ |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, |
| rw); |
| #ifdef KDTRACE_HOOKS |
| sleep_time -= lockstat_nsecs(); |
| #endif |
| turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); |
| #ifdef KDTRACE_HOOKS |
| sleep_time += lockstat_nsecs(); |
| sleep_cnt++; |
| #endif |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p resuming from turnstile", |
| __func__, rw); |
| #ifdef ADAPTIVE_RWLOCKS |
| spintries = 0; |
| #endif |
| } |
| LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, rw, contested, |
| waittime, file, line); |
| #ifdef KDTRACE_HOOKS |
| if (sleep_time) |
| LOCKSTAT_RECORD1(LS_RW_WLOCK_BLOCK, rw, sleep_time); |
| |
| /* |
| * Record only the loops spinning and not sleeping. |
| */ |
| if (spin_cnt > sleep_cnt) |
| LOCKSTAT_RECORD1(LS_RW_WLOCK_SPIN, rw, (spin_cnt - sleep_cnt)); |
| #endif |
| } |
| |
| /* |
| * This function is called if the first try at releasing a write lock failed. |
| * This means that one of the 2 waiter bits must be set indicating that at |
| * least one thread is waiting on this lock. |
| */ |
| void |
| _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) |
| { |
| struct turnstile *ts; |
| uintptr_t v; |
| int queue; |
| |
| if (rw_wlocked(rw) && rw_recursed(rw)) { |
| rw->rw_recurse--; |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); |
| return; |
| } |
| |
| KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), |
| ("%s: neither of the waiter flags are set", __func__)); |
| |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); |
| |
| turnstile_chain_lock(&rw->lock_object); |
| ts = turnstile_lookup(&rw->lock_object); |
| MPASS(ts != NULL); |
| |
| /* |
| * Use the same algo as sx locks for now. Prefer waking up shared |
| * waiters if we have any over writers. This is probably not ideal. |
| * |
| * 'v' is the value we are going to write back to rw_lock. If we |
| * have waiters on both queues, we need to preserve the state of |
| * the waiter flag for the queue we don't wake up. For now this is |
| * hardcoded for the algorithm mentioned above. |
| * |
| * In the case of both readers and writers waiting we wakeup the |
| * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a |
| * new writer comes in before a reader it will claim the lock up |
| * above. There is probably a potential priority inversion in |
| * there that could be worked around either by waking both queues |
| * of waiters or doing some complicated lock handoff gymnastics. |
| */ |
| v = RW_UNLOCKED; |
| if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) { |
| queue = TS_EXCLUSIVE_QUEUE; |
| v |= (rw->rw_lock & RW_LOCK_READ_WAITERS); |
| } else |
| queue = TS_SHARED_QUEUE; |
| |
| /* Wake up all waiters for the specific queue. */ |
| if (LOCK_LOG_TEST(&rw->lock_object, 0)) |
| CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, |
| queue == TS_SHARED_QUEUE ? "read" : "write"); |
| turnstile_broadcast(ts, queue); |
| atomic_store_rel_ptr(&rw->rw_lock, v); |
| turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); |
| turnstile_chain_unlock(&rw->lock_object); |
| } |
| |
| /* |
| * Attempt to do a non-blocking upgrade from a read lock to a write |
| * lock. This will only succeed if this thread holds a single read |
| * lock. Returns true if the upgrade succeeded and false otherwise. |
| */ |
| int |
| _rw_try_upgrade(struct rwlock *rw, const char *file, int line) |
| { |
| uintptr_t v, x, tid; |
| struct turnstile *ts; |
| int success; |
| |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); |
| _rw_assert(rw, RA_RLOCKED, file, line); |
| |
| /* |
| * Attempt to switch from one reader to a writer. If there |
| * are any write waiters, then we will have to lock the |
| * turnstile first to prevent races with another writer |
| * calling turnstile_wait() before we have claimed this |
| * turnstile. So, do the simple case of no waiters first. |
| */ |
| tid = (uintptr_t)curthread; |
| success = 0; |
| for (;;) { |
| v = rw->rw_lock; |
| if (RW_READERS(v) > 1) |
| break; |
| if (!(v & RW_LOCK_WAITERS)) { |
| success = atomic_cmpset_ptr(&rw->rw_lock, v, tid); |
| if (!success) |
| continue; |
| break; |
| } |
| |
| /* |
| * Ok, we think we have waiters, so lock the turnstile. |
| */ |
| ts = turnstile_trywait(&rw->lock_object); |
| v = rw->rw_lock; |
| if (RW_READERS(v) > 1) { |
| turnstile_cancel(ts); |
| break; |
| } |
| /* |
| * Try to switch from one reader to a writer again. This time |
| * we honor the current state of the waiters flags. |
| * If we obtain the lock with the flags set, then claim |
| * ownership of the turnstile. |
| */ |
| x = rw->rw_lock & RW_LOCK_WAITERS; |
| success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x); |
| if (success) { |
| if (x) |
| turnstile_claim(ts); |
| else |
| turnstile_cancel(ts); |
| break; |
| } |
| turnstile_cancel(ts); |
| } |
| LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); |
| if (success) { |
| curthread->td_rw_rlocks--; |
| WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, |
| file, line); |
| LOCKSTAT_RECORD0(LS_RW_TRYUPGRADE_UPGRADE, rw); |
| } |
| return (success); |
| } |
| |
| /* |
| * Downgrade a write lock into a single read lock. |
| */ |
| void |
| _rw_downgrade(struct rwlock *rw, const char *file, int line) |
| { |
| struct turnstile *ts; |
| uintptr_t tid, v; |
| int rwait, wwait; |
| |
| KASSERT(rw->rw_lock != RW_DESTROYED, |
| ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); |
| _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); |
| #ifndef INVARIANTS |
| if (rw_recursed(rw)) |
| panic("downgrade of a recursed lock"); |
| #endif |
| |
| WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); |
| |
| /* |
| * Convert from a writer to a single reader. First we handle |
| * the easy case with no waiters. If there are any waiters, we |
| * lock the turnstile and "disown" the lock. |
| */ |
| tid = (uintptr_t)curthread; |
| if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) |
| goto out; |
| |
| /* |
| * Ok, we think we have waiters, so lock the turnstile so we can |
| * read the waiter flags without any races. |
| */ |
| turnstile_chain_lock(&rw->lock_object); |
| v = rw->rw_lock & RW_LOCK_WAITERS; |
| rwait = v & RW_LOCK_READ_WAITERS; |
| wwait = v & RW_LOCK_WRITE_WAITERS; |
| MPASS(rwait | wwait); |
| |
| /* |
| * Downgrade from a write lock while preserving waiters flag |
| * and give up ownership of the turnstile. |
| */ |
| ts = turnstile_lookup(&rw->lock_object); |
| MPASS(ts != NULL); |
| if (!wwait) |
| v &= ~RW_LOCK_READ_WAITERS; |
| atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v); |
| /* |
| * Wake other readers if there are no writers pending. Otherwise they |
| * won't be able to acquire the lock anyway. |
| */ |
| if (rwait && !wwait) { |
| turnstile_broadcast(ts, TS_SHARED_QUEUE); |
| turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); |
| } else |
| turnstile_disown(ts); |
| turnstile_chain_unlock(&rw->lock_object); |
| out: |
| curthread->td_rw_rlocks++; |
| LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); |
| LOCKSTAT_RECORD0(LS_RW_DOWNGRADE_DOWNGRADE, rw); |
| } |
| |
| #ifdef INVARIANT_SUPPORT |
| #ifndef INVARIANTS |
| #undef _rw_assert |
| #endif |
| |
| /* |
| * In the non-WITNESS case, rw_assert() can only detect that at least |
| * *some* thread owns an rlock, but it cannot guarantee that *this* |
| * thread owns an rlock. |
| */ |
| void |
| _rw_assert(struct rwlock *rw, int what, const char *file, int line) |
| { |
| |
| if (panicstr != NULL) |
| return; |
| switch (what) { |
| case RA_LOCKED: |
| case RA_LOCKED | RA_RECURSED: |
| case RA_LOCKED | RA_NOTRECURSED: |
| case RA_RLOCKED: |
| #ifdef WITNESS |
| witness_assert(&rw->lock_object, what, file, line); |
| #else |
| /* |
| * If some other thread has a write lock or we have one |
| * and are asserting a read lock, fail. Also, if no one |
| * has a lock at all, fail. |
| */ |
| if (rw->rw_lock == RW_UNLOCKED || |
| (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || |
| rw_wowner(rw) != curthread))) |
| panic("Lock %s not %slocked @ %s:%d\n", |
| rw->lock_object.lo_name, (what == RA_RLOCKED) ? |
| "read " : "", file, line); |
| |
| if (!(rw->rw_lock & RW_LOCK_READ)) { |
| if (rw_recursed(rw)) { |
| if (what & RA_NOTRECURSED) |
| panic("Lock %s recursed @ %s:%d\n", |
| rw->lock_object.lo_name, file, |
| line); |
| } else if (what & RA_RECURSED) |
| panic("Lock %s not recursed @ %s:%d\n", |
| rw->lock_object.lo_name, file, line); |
| } |
| #endif |
| break; |
| case RA_WLOCKED: |
| case RA_WLOCKED | RA_RECURSED: |
| case RA_WLOCKED | RA_NOTRECURSED: |
| if (rw_wowner(rw) != curthread) |
| panic("Lock %s not exclusively locked @ %s:%d\n", |
| rw->lock_object.lo_name, file, line); |
| if (rw_recursed(rw)) { |
| if (what & RA_NOTRECURSED) |
| panic("Lock %s recursed @ %s:%d\n", |
| rw->lock_object.lo_name, file, line); |
| } else if (what & RA_RECURSED) |
| panic("Lock %s not recursed @ %s:%d\n", |
| rw->lock_object.lo_name, file, line); |
| break; |
| case RA_UNLOCKED: |
| #ifdef WITNESS |
| witness_assert(&rw->lock_object, what, file, line); |
| #else |
| /* |
| * If we hold a write lock fail. We can't reliably check |
| * to see if we hold a read lock or not. |
| */ |
| if (rw_wowner(rw) == curthread) |
| panic("Lock %s exclusively locked @ %s:%d\n", |
| rw->lock_object.lo_name, file, line); |
| #endif |
| break; |
| default: |
| panic("Unknown rw lock assertion: %d @ %s:%d", what, file, |
| line); |
| } |
| } |
| #endif /* INVARIANT_SUPPORT */ |
| #endif //0 |
| |
| void rw_wlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_wlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| host_pthread_rwlock_wlock((void*)&rw->lock_object); |
| |
| } |
| |
| void rw_wunlock(struct rwlock *rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_wunlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| host_pthread_rwlock_wunlock((void*)&rw->lock_object); |
| } |
| |
| void rw_rlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_rlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| host_pthread_rwlock_rlock((void*)&rw->lock_object); |
| } |
| |
| void rw_runlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_runlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| host_pthread_rwlock_runlock((void*)&rw->lock_object); |
| } |
| |
| int rw_try_rlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_try_rlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| return host_pthread_rwlock_tryrlock((void*)&rw->lock_object); |
| } |
| |
| |
| int rw_try_upgrade(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_try_upgrade %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| //host_pthread_rwlock_wlock(rw->lock_object->ext_lock); |
| return 0; |
| } |
| int rw_try_wlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_try_wlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| return host_pthread_rwlock_trywlock((void*)&rw->lock_object); |
| } |
| |
| void rw_downgrade(struct rwlock *rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_downgrade %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| //host_pthread_rwlock_wlock(rw->lock_object->ext_lock); |
| } |
| |
| void rw_unlock(struct rwlock* rw) |
| { |
| UPTCP_RWLOCK_DEBUG_PRINT("rw_unlock %s, recurse = %d\n", |
| rw->lock_object.lo_name, rw->lock_object.lo_data); |
| |
| host_pthread_rwlock_unlock((void*)&rw->lock_object); |
| } |
| |
| |
| #ifdef DDB |
| void |
| db_show_rwlock(struct lock_object *lock) |
| { |
| struct rwlock *rw; |
| struct thread *td; |
| |
| rw = (struct rwlock *)lock; |
| |
| db_printf(" state: "); |
| if (rw->rw_lock == RW_UNLOCKED) |
| db_printf("UNLOCKED\n"); |
| else if (rw->rw_lock == RW_DESTROYED) { |
| db_printf("DESTROYED\n"); |
| return; |
| } else if (rw->rw_lock & RW_LOCK_READ) |
| db_printf("RLOCK: %ju locks\n", |
| (uintmax_t)(RW_READERS(rw->rw_lock))); |
| else { |
| td = rw_wowner(rw); |
| db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, |
| td->td_tid, td->td_proc->p_pid, td->td_name); |
| if (rw_recursed(rw)) |
| db_printf(" recursed: %u\n", rw->rw_recurse); |
| } |
| db_printf(" waiters: "); |
| switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { |
| case RW_LOCK_READ_WAITERS: |
| db_printf("readers\n"); |
| break; |
| case RW_LOCK_WRITE_WAITERS: |
| db_printf("writers\n"); |
| break; |
| case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: |
| db_printf("readers and writers\n"); |
| break; |
| default: |
| db_printf("none\n"); |
| break; |
| } |
| } |
| |
| #endif |