Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761920AbXHDGk1 (ORCPT ); Sat, 4 Aug 2007 02:40:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753990AbXHDGkR (ORCPT ); Sat, 4 Aug 2007 02:40:17 -0400 Received: from 216-99-217-87.dsl.aracnet.com ([216.99.217.87]:40170 "EHLO sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755049AbXHDGkQ (ORCPT ); Sat, 4 Aug 2007 02:40:16 -0400 Date: Fri, 3 Aug 2007 23:39:47 -0700 From: Chris Wright To: Oleg Nesterov Cc: Manfred Spraul , Andrew Morton , linux-kernel@vger.kernel.org, Roland McGrath , "Agarwal, Lomesh" Subject: [PATCH] Use ERESTART_RESTARTBLOCK if poll() is interrupted by a signal (was: Re: [PATCH] Use ERESTARTNOHAND if poll() is interrupted by a signal) Message-ID: <20070804063947.GQ3672@sequoia.sous-sol.org> References: <200707291705.l6TH554a003344@colorfullife.mysite.adiungo.com> <20070730163538.67b256da.akpm@linux-foundation.org> <46AF9C2D.70808@colorfullife.com> <20070731210817.GA97@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070731210817.GA97@tv-sign.ru> User-Agent: Mutt/1.5.14 (2007-02-12) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3362 Lines: 99 * Oleg Nesterov (oleg@tv-sign.ru) wrote: > What we need is ERESTART_RESTARTBLOCK, and restart_block.arg2 should > have the new timeout value, which takes the time we already slept > into account. This passes my simple 32-bit and 64-bit testing. See any issues with this one? thanks, -chris -- Subject: [PATCH] Use ERESTART_RESTARTBLOCK if poll() is interrupted by a signal From: Chris Wright Lomesh reported poll returning EINTR during suspend/resume cycle. This is caused by the STOP/CONT cycle that the freezer uses, generating a pending signal for what in effect is an ignored signal. In general poll is a little eager in returning EINTR, when it could try not bother userspace and simply restart the syscall. Both select and ppoll do use ERESTARTNOHAND to restart the syscall. Oleg points out that simply using ERESTARTNOHAND will cause poll to restart with original timeout value. which could ultimately lead to process never returning to userspace. Instead use ERESTART_RESTARTBLOCK, and restart poll with updated timeout value. Inspired by Manfred's use ERESTARTNOHAND in poll patch. Cc: Manfred Spraul Cc: Oleg Nesterov Cc: Andrew Morton Cc: Roland McGrath Cc: "Agarwal, Lomesh" Signed-off-by: Chris Wright --- Patch against git-7a883eaf fs/select.c | 34 +++++++++++++++++++++++++++++++++- 1 files changed, 33 insertions(+), 1 deletions(-) diff --git a/fs/select.c b/fs/select.c index a974082..50e6d8e 100644 --- a/fs/select.c +++ b/fs/select.c @@ -736,10 +736,29 @@ out_fds: return err; } +long do_restart_poll(struct restart_block *restart_block) +{ + struct pollfd __user *ufds = (struct pollfd __user*)restart_block->arg0; + int nfds = restart_block->arg1; + s64 timeout = ((s64)restart_block->arg3<<32) | (s64)restart_block->arg2; + int ret; + + restart_block->fn = do_no_restart_syscall; + ret = do_sys_poll(ufds, nfds, &timeout); + if (ret == -EINTR) { + restart_block->fn = do_restart_poll; + restart_block->arg2 = timeout & 0xFFFFFFFF; + restart_block->arg3 = timeout >> 32; + ret = -ERESTART_RESTARTBLOCK; + } + return ret; +} + asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds, long timeout_msecs) { s64 timeout_jiffies; + int ret; if (timeout_msecs > 0) { #if HZ > 1000 @@ -754,7 +773,20 @@ asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds, timeout_jiffies = timeout_msecs; } - return do_sys_poll(ufds, nfds, &timeout_jiffies); + ret = do_sys_poll(ufds, nfds, &timeout_jiffies); + if (ret == -EINTR) { + if (timeout_msecs > 0) { + struct restart_block *restart_block; + restart_block = ¤t_thread_info()->restart_block; + restart_block->fn = do_restart_poll; + restart_block->arg0 = (unsigned long)ufds; + restart_block->arg1 = nfds; + restart_block->arg2 = timeout_jiffies & 0xFFFFFFFF; + restart_block->arg3 = timeout_jiffies >> 32; + ret = -ERESTART_RESTARTBLOCK; + } + } + return ret; } #ifdef TIF_RESTORE_SIGMASK - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/