linux-kernel - Re: [patch] exclude sync signals from signalfd sets

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Date:	Wed, 20 Jun 2007 13:12:47 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [patch] exclude sync signals from signalfd sets

On Wed, 20 Jun 2007, Linus Torvalds wrote:

> 
> 
> On Wed, 20 Jun 2007, Davide Libenzi wrote:
> > 
> > The following patch excludes synchronous signals from being dequeued
> > by a signalfd.
> 
> I really prefer the current code. Listign special cases is just ugly. Just 
> make it so that thread-local signals stay thread-local, and it's all good.

Hmm, I thought the behaviour implemented by the patch was pretty clean. 
But anyway, if we leave the current code (as it is in your current tree), 
we need the patch below to avoid spurious poll returns.



- 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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