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Commit 91593504 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 24ec839c

fs/proc/array.c

+4 −12
Original line number Diff line number Diff line
@@ -346,20 +346,13 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) 
	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 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) 
		unlock_task_sighand(task, &flags);

	}

	rcu_read_unlock();

	mutex_unlock(&tty_mutex);



	if (!whole || num_threads<2)

		wchan = get_wchan(task);