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[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>
This commit is contained in:
Oleg Nesterov 2006-12-08 02:36:07 -08:00 committed by Linus Torvalds
parent 24ec839c43
commit 9159350412
1 changed files with 3 additions and 11 deletions
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14
fs/proc/array.c
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@ -346,20 +346,13 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
sigemptyset(&sigcatch); sigemptyset(&sigcatch);
cutime = cstime = utime = stime = cputime_zero; cutime = cstime = utime = stime = cputime_zero;
mutex_lock(&tty_mutex);
rcu_read_lock(); rcu_read_lock();
if (lock_task_sighand(task, &flags)) { if (lock_task_sighand(task, &flags)) {
struct signal_struct *sig = task->signal; struct signal_struct *sig = task->signal;
struct tty_struct *tty = sig->tty;
if (tty) { if (sig->tty) {
/* tty_pgrp = sig->tty->pgrp;
* sig->tty is not stable, but tty_mutex tty_nr = new_encode_dev(tty_devnum(sig->tty));
* protects us from release_dev(tty)
*/
barrier();
tty_pgrp = tty->pgrp;
tty_nr = new_encode_dev(tty_devnum(tty));
} }
num_threads = atomic_read(&sig->count); num_threads = atomic_read(&sig->count);
@ -395,7 +388,6 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
unlock_task_sighand(task, &flags); unlock_task_sighand(task, &flags);
} }
rcu_read_unlock(); rcu_read_unlock();
mutex_unlock(&tty_mutex);
if (!whole || num_threads<2) if (!whole || num_threads<2)
wchan = get_wchan(task); wchan = get_wchan(task);