linux-kernel - [patch] avoid spurious POLLIN returns in signalfd

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Date:	Wed, 20 Jun 2007 14:54:17 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [patch] avoid spurious POLLIN returns in signalfd

The new code in kernel/signal.c does not allow fetching private signals 
from another task. This patch avoid spurious POLLIN returns from a 
signalfd poll(2) operation.



Signed-off-by: Davide Libenzi <davidel@...ilserver.org>


- Davide


---
 fs/signalfd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.mod/fs/signalfd.c
===================================================================
--- linux-2.6.mod.orig/fs/signalfd.c	2007-06-20 13:08:25.000000000 -0700
+++ linux-2.6.mod/fs/signalfd.c	2007-06-20 13:09:00.000000000 -0700
@@ -133,7 +133,8 @@
 	 * the peer disconnects.
 	 */
 	if (signalfd_lock(ctx, &lk)) {
-		if (next_signal(&lk.tsk->pending, &ctx->sigmask) > 0 ||
+		if ((lk.tsk == current &&
+		     next_signal(&lk.tsk->pending, &ctx->sigmask) > 0) ||
 		    next_signal(&lk.tsk->signal->shared_pending,
 				&ctx->sigmask) > 0)
 			events |= POLLIN;
-
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