linux-kernel - [PATCH] wait_task_zombie: don't fight with non-existing race with a dying ptracee

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Message-ID: <20070817153740.GA1098@tv-sign.ru>
Date:	Fri, 17 Aug 2007 19:37:40 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Roland McGrath <roland@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] wait_task_zombie: don't fight with non-existing race with a dying ptracee

(textually depends on wait_task_zombie-remove-unneeded-child-signal-check.patch)

The "p->exit_signal == -1 && p->ptrace == 0" check and the comment are bogus.
We already did exactly the same check in eligible_child(), we did not drop
tasklist_lock since then, and both variables need write_lock(tasklist) to be
changed.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- t/kernel/exit.c~1_WTZ_NORACE	2007-08-17 17:31:59.000000000 +0400
+++ t/kernel/exit.c	2007-08-17 18:56:31.000000000 +0400
@@ -1210,13 +1210,6 @@ static int wait_task_zombie(struct task_
 		BUG_ON(state != EXIT_DEAD);
 		return 0;
 	}
-	if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
-		/*
-		 * This can only happen in a race with a ptraced thread
-		 * dying on another processor.
-		 */
-		return 0;
-	}
 
 	/* traced means p->ptrace, but not vice versa */
 	traced = (p->real_parent != p->parent);

-
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