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Commit 7d7185c8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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[PATCH] sys_times: don't take tasklist_lock 



sys_times: don't take tasklist_lock

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5876700c

kernel/sys.c

+1 −12
Original line number Diff line number Diff line
@@ -1206,7 +1206,7 @@ asmlinkage long sys_times(struct tms __user * tbuf) 
		struct task_struct *t;

		cputime_t utime, stime, cutime, cstime;



		read_lock(&tasklist_lock);

		spin_lock_irq(&tsk->sighand->siglock);

		utime = tsk->signal->utime;

		stime = tsk->signal->stime;

		t = tsk;
@@ -1216,20 +1216,9 @@ asmlinkage long sys_times(struct tms __user * tbuf) 
			t = next_thread(t);

		} while (t != tsk);



		/*

		 * While we have tasklist_lock read-locked, no dying thread

		 * can be updating current->signal->[us]time.  Instead,

		 * we got their counts included in the live thread loop.

		 * However, another thread can come in right now and

		 * do a wait call that updates current->signal->c[us]time.

		 * To make sure we always see that pair updated atomically,

		 * we take the siglock around fetching them.

		 */

		spin_lock_irq(&tsk->sighand->siglock);

		cutime = tsk->signal->cutime;

		cstime = tsk->signal->cstime;

		spin_unlock_irq(&tsk->sighand->siglock);

		read_unlock(&tasklist_lock);



		tmp.tms_utime = cputime_to_clock_t(utime);

		tmp.tms_stime = cputime_to_clock_t(stime);