Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933402Ab1CaJbm (ORCPT ); Thu, 31 Mar 2011 05:31:42 -0400 Received: from hera.kernel.org ([140.211.167.34]:40061 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933339Ab1CaJbk (ORCPT ); Thu, 31 Mar 2011 05:31:40 -0400 Date: Thu, 31 Mar 2011 09:30:59 GMT From: tip-bot for Davidlohr Bueso Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, andi@firstfloor.org, dave@gnu.org, paulmck@linux.vnet.ibm.com, zdenek.kabelac@gmail.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, andi@firstfloor.org, dave@gnu.org, paulmck@linux.vnet.ibm.com, zdenek.kabelac@gmail.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <1301537604.2140.21.camel@offworld> References: <1301537604.2140.21.camel@offworld> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86, mce: Fix RCU lockdep from mce_poll() Message-ID: Git-Commit-ID: 706453b0d1fabf4dccbcffa29356d0dd6ab9afb9 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 31 Mar 2011 09:31:01 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3268 Lines: 78 Commit-ID: 706453b0d1fabf4dccbcffa29356d0dd6ab9afb9 Gitweb: http://git.kernel.org/tip/706453b0d1fabf4dccbcffa29356d0dd6ab9afb9 Author: Davidlohr Bueso AuthorDate: Wed, 30 Mar 2011 23:13:24 -0300 Committer: Ingo Molnar CommitDate: Thu, 31 Mar 2011 11:06:08 +0200 x86, mce: Fix RCU lockdep from mce_poll() Based on the following message: =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- arch/x86/kernel/cpu/mcheck/mce.c:1628 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 no locks held by mcelog/2350. stack backtrace: Pid: 2350, comm: mcelog Tainted: G W 2.6.37-rc1+ #7 Call Trace: [] lockdep_rcu_dereference+0xa4/0xc0 [] mce_poll+0xa9/0xd0 [] do_sys_poll+0x275/0x550 [] ? __pollwait+0x0/0xf0 [] ? pollwake+0x0/0x60 [] ? pollwake+0x0/0x60 [] ? rcu_read_lock_held+0x2c/0x30 [] ? radix_tree_lookup_element+0xda/0x100 [] ? __do_fault+0x128/0x470 [] ? filemap_fault+0xdb/0x4e0 [] ? unlock_page+0x25/0x30 [] ? sigprocmask+0x3f/0x100 [] ? _raw_spin_unlock_irq+0x2b/0x60 [] ? trace_hardirqs_on_caller+0x13d/0x180 [] ? trace_hardirqs_on+0xd/0x10 [] ? _raw_spin_unlock_irq+0x2b/0x60 [] sys_ppoll+0x47/0x190 [] ? trace_hardirqs_on_caller+0x13d/0x180 [] ? trace_hardirqs_on_thunk+0x3a/0x3f [] system_call_fastpath+0x16/0x1b This code is simply checking the value of the pointer, and therefore need not protect any actual dereferences. Replace rcu_dereference_check_mce() with rcu_dereference_index_check(). Signed-off-by: Davidlohr Bueso Acked-by: Paul E. McKenney Cc: Zdenek Kabelac Cc: Andi Kleen LKML-Reference: <1301537604.2140.21.camel@offworld> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/mcheck/mce.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 5a05ef6..a2d664f 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1626,7 +1626,7 @@ out: static unsigned int mce_poll(struct file *file, poll_table *wait) { poll_wait(file, &mce_wait, wait); - if (rcu_dereference_check_mce(mcelog.next)) + if (rcu_dereference_index_check(mcelog.next, rcu_read_lock_sched_held())) return POLLIN | POLLRDNORM; if (!mce_apei_read_done && apei_check_mce()) return POLLIN | POLLRDNORM; -- 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/