[PATCH] proc: convert task_sig() to use lock_task_sighand()

lock_task_sighand() can take ->siglock without holding tasklist_lock.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index c0e554971df0..279fbf542c88 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -244,6 +244,7 @@ static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign,
 
 static inline char * task_sig(struct task_struct *p, char *buffer)
 {
+        unsigned long flags;
         sigset_t pending, shpending, blocked, ignored, caught;
         int num_threads = 0;
         unsigned long qsize = 0;
@@ -255,10 +256,8 @@ static inline char * task_sig(struct task_struct *p, char *buffer)
         sigemptyset(&ignored);
         sigemptyset(&caught);
 
-        /* Gather all the data with the appropriate locks held */
-        read_lock(&tasklist_lock);
-        if (p->sighand) {
-                spin_lock_irq(&p->sighand->siglock);
+        rcu_read_lock();
+        if (lock_task_sighand(p, &flags)) {
                 pending = p->pending.signal;
                 shpending = p->signal->shared_pending.signal;
                 blocked = p->blocked;
@@ -266,9 +265,9 @@ static inline char * task_sig(struct task_struct *p, char *buffer)
                 num_threads = atomic_read(&p->signal->count);
                 qsize = atomic_read(&p->user->sigpending);
                 qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur;
-                spin_unlock_irq(&p->sighand->siglock);
+                unlock_task_sighand(p, &flags);
         }
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
 
         buffer += sprintf(buffer, "Threads:\t%d\n", num_threads);
         buffer += sprintf(buffer, "SigQ:\t%lu/%lu\n", qsize, qlim);