Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753598Ab3DSTBf (ORCPT ); Fri, 19 Apr 2013 15:01:35 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:53962 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041Ab3DSTBe (ORCPT ); Fri, 19 Apr 2013 15:01:34 -0400 Date: Fri, 19 Apr 2013 12:01:24 -0700 From: "Paul E. McKenney" To: a.p.zijlstra@chello.nl, paulus@samba.org, mingo@redhat.com, acme@ghostprotocols.net Cc: linux-kernel@vger.kernel.org, ajax@redhat.com, gusld@br.ibm.com Subject: [PATCH] events: Protect access via task_subsys_state_check() Message-ID: <20130419190124.GA8638@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13041919-7182-0000-0000-000006515B2C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2607 Lines: 61 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 [ 953.267751] [c0000001f0d1bbc0] [c00000000027e724] .search_binary_handler+0x254/0x680 [ 953.267758] [c0000001f0d1bca0] [c0000000002800dc] .do_execve_common.isra.17+0x76c/0x860 [ 953.267764] [c0000001f0d1bd90] [c000000000280698] .SyS_execve+0x58/0x90 [ 953.267771] [c0000001f0d1be30] [c000000000009e60] syscall_exit+0x0/0x98 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 Tested-by: Gustavo Luiz Duarte diff --git a/kernel/events/core.c b/kernel/events/core.c index b0cd865..8db9551 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4593,6 +4593,7 @@ 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) @@ -4600,6 +4601,7 @@ 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/