From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755951Ab3A0OgO (ORCPT ); Sun, 27 Jan 2013 09:36:14 -0500 Received: from terminus.zytor.com ([198.137.202.10]:60229 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754965Ab3A0OgL (ORCPT ); Sun, 27 Jan 2013 09:36:11 -0500 Date: Sun, 27 Jan 2013 06:35:50 -0800 From: tip-bot for Wang YanQing Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, udknight@gmail.com, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, stable@kernel.org, tglx@linutronix.de Reply-To: paulmck@linux.vnet.ibm.com, mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, stable@kernel.org, tglx@linutronix.de, udknight@gmail.com In-Reply-To: <20130126075357.GA3205@udknight> References: <20130126075357.GA3205@udknight> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] smp: Fix SMP function call empty cpu mask race Git-Commit-ID: c7b798525b50256c8084215a139fa40b0114bfcc X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Sun, 27 Jan 2013 06:35:57 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: c7b798525b50256c8084215a139fa40b0114bfcc Gitweb: http://git.kernel.org/tip/c7b798525b50256c8084215a139fa40b0114bfcc Author: Wang YanQing AuthorDate: Sat, 26 Jan 2013 15:53:57 +0800 Committer: Ingo Molnar CommitDate: Sun, 27 Jan 2013 13:29:14 +0100 smp: Fix SMP function call empty cpu mask race I get the following warning every day with v3.7, once or twice a day: [ 2235.186027] WARNING: at /mnt/sda7/kernel/linux/arch/x86/kernel/apic/ipi.c:109 default_send_IPI_mask_logical+0x2f/0xb8() As explained by Linus as well: | | Once we've done the "list_add_rcu()" to add it to the | queue, we can have (another) IPI to the target CPU that can | now see it and clear the mask. | | So by the time we get to actually send the IPI, the mask might | have been cleared by another IPI. | This patch also fixes a system hang problem, if the data->cpumask gets cleared after passing this point: if (WARN_ONCE(!mask, "empty IPI mask")) return; then the problem in commit 83d349f35e1a ("x86: don't send an IPI to the empty set of CPU's") will happen again. Signed-off-by: Wang YanQing Acked-by: Linus Torvalds Cc: Paul E. McKenney Cc: Andrew Morton Cc: peterz@infradead.org Cc: mina86@mina86.org Cc: srivatsa.bhat@linux.vnet.ibm.com Cc: Link: http://lkml.kernel.org/r/20130126075357.GA3205@udknight [ Tidied up the changelog and the comment in the code. ] Signed-off-by: Ingo Molnar --- kernel/smp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/smp.c b/kernel/smp.c index 29dd40a..93e576e 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -33,6 +33,7 @@ struct call_function_data { struct call_single_data csd; atomic_t refs; cpumask_var_t cpumask; + cpumask_var_t cpumask_ipi; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); @@ -526,6 +527,12 @@ void smp_call_function_many(const struct cpumask *mask, return; } + /* + * After we put an entry into the list, data->cpumask + * may be cleared again when another CPU sends another IPI for + * a SMP function call, so data->cpumask will be zero. + */ + cpumask_copy(data->cpumask_ipi, data->cpumask); raw_spin_lock_irqsave(&call_function.lock, flags); /* * Place entry at the _HEAD_ of the list, so that any cpu still @@ -549,7 +556,7 @@ void smp_call_function_many(const struct cpumask *mask, smp_mb(); /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(data->cpumask); + arch_send_call_function_ipi_mask(data->cpumask_ipi); /* Optionally wait for the CPUs to complete */ if (wait)