Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753521Ab3DUMvU (ORCPT ); Sun, 21 Apr 2013 08:51:20 -0400 Received: from terminus.zytor.com ([198.137.202.10]:40721 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751012Ab3DUMvS (ORCPT ); Sun, 21 Apr 2013 08:51:18 -0400 Date: Sun, 21 Apr 2013 05:51:01 -0700 From: "tip-bot for Paul E. McKenney" Message-ID: Cc: gusld@br.ibm.com, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de, ajax@redhat.com Reply-To: mingo@kernel.org, hpa@zytor.com, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, gusld@br.ibm.com, tglx@linutronix.de, ajax@redhat.com In-Reply-To: <20130419190124.GA8638@linux.vnet.ibm.com> References: <20130419190124.GA8638@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] events: Protect access via task_subsys_state_check() Git-Commit-ID: c79aa0d96548aee50570209eb2d45c8f4ac49230 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, 21 Apr 2013 05:51:07 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2917 Lines: 74 Commit-ID: c79aa0d96548aee50570209eb2d45c8f4ac49230 Gitweb: http://git.kernel.org/tip/c79aa0d96548aee50570209eb2d45c8f4ac49230 Author: Paul E. McKenney AuthorDate: Fri, 19 Apr 2013 12:01:24 -0700 Committer: Ingo Molnar CommitDate: Sun, 21 Apr 2013 11:21:39 +0200 events: Protect access via task_subsys_state_check() The following RCU splat indicates lack of RCU protection: [ 953.267649] =============================== [ 953.267652] [ INFO: suspicious RCU usage. ] [ 953.267657] 3.9.0-0.rc6.git2.4.fc19.ppc64p7 #1 Not tainted [ 953.267661] ------------------------------- [ 953.267664] include/linux/cgroup.h:534 suspicious rcu_dereference_check() usage! [ 953.267669] [ 953.267669] other info that might help us debug this: [ 953.267669] [ 953.267675] [ 953.267675] rcu_scheduler_active = 1, debug_locks = 0 [ 953.267680] 1 lock held by glxgears/1289: [ 953.267683] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] .prepare_bprm_creds+0x34/0xa0 [ 953.267700] [ 953.267700] stack backtrace: [ 953.267704] Call Trace: [ 953.267709] [c0000001f0d1b6e0] [c000000000016e30] .show_stack+0x130/0x200 (unreliable) [ 953.267717] [c0000001f0d1b7b0] [c0000000001267f8] .lockdep_rcu_suspicious+0x138/0x180 [ 953.267724] [c0000001f0d1b840] [c0000000001d43a4] .perf_event_comm+0x4c4/0x690 [ 953.267731] [c0000001f0d1b950] [c00000000027f6e4] .set_task_comm+0x84/0x1f0 [ 953.267737] [c0000001f0d1b9f0] [c000000000280414] .setup_new_exec+0x94/0x220 [ 953.267744] [c0000001f0d1ba70] [c0000000002f665c] .load_elf_binary+0x58c/0x19b0 ... This commit therefore adds the required RCU read-side critical section to perf_event_comm(). Reported-by: Adam Jackson Signed-off-by: Paul E. McKenney Cc: a.p.zijlstra@chello.nl Cc: paulus@samba.org Cc: acme@ghostprotocols.net Link: http://lkml.kernel.org/r/20130419190124.GA8638@linux.vnet.ibm.com Signed-off-by: Ingo Molnar Tested-by: Gustavo Luiz Duarte --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 4d3124b..9fcb094 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4596,6 +4596,7 @@ void perf_event_comm(struct task_struct *task) struct perf_event_context *ctx; int ctxn; + rcu_read_lock(); for_each_task_context_nr(ctxn) { ctx = task->perf_event_ctxp[ctxn]; if (!ctx) @@ -4603,6 +4604,7 @@ void perf_event_comm(struct task_struct *task) perf_event_enable_on_exec(ctx); } + rcu_read_unlock(); if (!atomic_read(&nr_comm_events)) return; -- 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/