[PATCH] signal, procfs: some lock_task_sighand() users do not need rcu_read_lock()
lock_task_sighand() make sure task->sighand is being protected,
so we do not need rcu_read_lock().
[ exec() will get task->sighand->siglock before change task->sighand! ]
But code using rcu_read_lock() _just_ to protect lock_task_sighand()
only appear in procfs. (and some code in procfs use lock_task_sighand()
without such redundant protection.)
Other subsystem may put lock_task_sighand() into rcu_read_lock()
critical region, but these rcu_read_lock() are used for protecting
"for_each_process()", "find_task_by_vpid()" etc. , not for protecting
lock_task_sighand().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
[ok from Oleg]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 71c9be5..1c8d7b5 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -261,7 +261,6 @@
sigemptyset(&ignored);
sigemptyset(&caught);
- rcu_read_lock();
if (lock_task_sighand(p, &flags)) {
pending = p->pending.signal;
shpending = p->signal->shared_pending.signal;
@@ -272,7 +271,6 @@
qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur;
unlock_task_sighand(p, &flags);
}
- rcu_read_unlock();
seq_printf(m, "Threads:\t%d\n", num_threads);
seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a28840b..bb63fa1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -164,7 +164,6 @@
static int get_nr_threads(struct task_struct *tsk)
{
- /* Must be called with the rcu_read_lock held */
unsigned long flags;
int count = 0;
@@ -471,14 +470,10 @@
struct rlimit rlim[RLIM_NLIMITS];
- rcu_read_lock();
- if (!lock_task_sighand(task,&flags)) {
- rcu_read_unlock();
+ if (!lock_task_sighand(task, &flags))
return 0;
- }
memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
unlock_task_sighand(task, &flags);
- rcu_read_unlock();
/*
* print the file header
@@ -3088,9 +3083,7 @@
generic_fillattr(inode, stat);
if (p) {
- rcu_read_lock();
stat->nlink += get_nr_threads(p);
- rcu_read_unlock();
put_task_struct(p);
}
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index bbe6b31..ad958c1 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -333,12 +333,10 @@
unsigned long flags;
int num_threads = 1;
- rcu_read_lock();
if (lock_task_sighand(p, &flags)) {
num_threads = atomic_read(&p->signal->count);
unlock_task_sighand(p, &flags);
}
- rcu_read_unlock();
SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads);
SEQ_printf(m,
