[PATCH] do_task_stat(): don't take tty_mutex
->signal->tty is protected by ->siglock, no need to take the global tty_mutex.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 25e917f..b0cd014 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -346,20 +346,13 @@
sigemptyset(&sigcatch);
cutime = cstime = utime = stime = cputime_zero;
- mutex_lock(&tty_mutex);
rcu_read_lock();
if (lock_task_sighand(task, &flags)) {
struct signal_struct *sig = task->signal;
- struct tty_struct *tty = sig->tty;
- if (tty) {
- /*
- * sig->tty is not stable, but tty_mutex
- * protects us from release_dev(tty)
- */
- barrier();
- tty_pgrp = tty->pgrp;
- tty_nr = new_encode_dev(tty_devnum(tty));
+ if (sig->tty) {
+ tty_pgrp = sig->tty->pgrp;
+ tty_nr = new_encode_dev(tty_devnum(sig->tty));
}
num_threads = atomic_read(&sig->count);
@@ -395,7 +388,6 @@
unlock_task_sighand(task, &flags);
}
rcu_read_unlock();
- mutex_unlock(&tty_mutex);
if (!whole || num_threads<2)
wchan = get_wchan(task);