Attachment 46481 Details for Bug 91434

[patch] itimer-fix1.patch

thread-itimer-fix1.patch (text/plain), 1.69 KB, created by Marcus Meissner on 2005-08-18 13:22:52 UTC

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Creator: Marcus Meissner

Created: 2005-08-18 13:22:52 UTC

Size: 1.69 KB

patch

obsolete

>From: Roland McGrath <roland@redhat.com>
>Date: Tue, 12 Jul 2005 20:58:27 +0000 (-0700)
>Subject: [PATCH] reset real_timer target on exec leader change
>X-Git-Tag: v2.6.13-rc3
>X-Git-Url: http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5323125031799a7fd8602ce150c3902aedfdcba6
>
>  [PATCH] reset real_timer target on exec leader change
>  
>  When a noninitial thread does exec, it becomes the new group leader.  If
>  there is a ITIMER_REAL timer running, it points at the old group leader and
>  when it fires it can follow a stale pointer.  The timer data needs to be
>  reset to point at the exec'ing thread that is becoming the group leader.
>  This has to synchronize with any concurrent firing of the timer to make
>  sure that it_real_fn can never run when the data points to a thread that
>  might have been reaped already.
>  
>  Signed-off-by: Roland McGrath <roland@redhat.com>
>  Signed-off-by: Andrew Morton <akpm@osdl.org>
>  Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>---
>
>--- a/fs/exec.c
>+++ b/fs/exec.c
>@@ -642,6 +642,18 @@ static inline int de_thread(struct task_
> 	count = 2;
> 	if (thread_group_leader(current))
> 		count = 1;
>+	else {
>+		/*
>+		 * The SIGALRM timer survives the exec, but needs to point
>+		 * at us as the new group leader now.  We have a race with
>+		 * a timer firing now getting the old leader, so we need to
>+		 * synchronize with any firing (by calling del_timer_sync)
>+		 * before we can safely let the old group leader die.
>+		 */
>+		sig->real_timer.data = (unsigned long)current;
>+		if (del_timer_sync(&sig->real_timer))
>+			add_timer(&sig->real_timer);
>+	}
> 	while (atomic_read(&sig->count) > count) {
> 		sig->group_exit_task = current;
> 		sig->notify_count = count;

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