From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753451AbaDESni (ORCPT ); Sat, 5 Apr 2014 14:43:38 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.232]:54113 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753347AbaDESnh (ORCPT ); Sat, 5 Apr 2014 14:43:37 -0400 Date: Sat, 5 Apr 2014 14:43:35 -0400 From: Steven Rostedt To: Sasha Levin Cc: linux-kernel@vger.kernel.org, Andrew Morton , Alexander Lam Subject: Re: [for-next][PATCH 14/14] tracing: Get trace_array ref counts when accessing trace files Message-ID: <20140405144335.5938984c@gandalf.local.home> In-Reply-To: <53401A3E.2090302@oracle.com> References: <20130702202216.623562799@goodmis.org> <20130702202427.455930200@goodmis.org> <53401A3E.2090302@oracle.com> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 05 Apr 2014 10:59:10 -0400 Sasha Levin wrote: > [ 5644.290783] Chain exists of: > trace_types_lock --> &pipe->mutex/1 --> &sig->cred_guard_mutex > > [ 5644.290783] Possible unsafe locking scenario: > [ 5644.290783] > [ 5644.290783] CPU0 CPU1 > [ 5644.290783] ---- ---- > [ 5644.290783] lock(&sig->cred_guard_mutex); > [ 5644.290783] lock(&pipe->mutex/1); > [ 5644.290783] lock(&sig->cred_guard_mutex); > [ 5644.290783] lock(trace_types_lock); Or I haven't done enough to trigger both paths in a single boot :-/ Anyway, I'm questioning the trace_types_lock being held throughout the entire path of tracing_buffers_splice_read(). I'll have to look deeper into this on Monday. If we can fine grain that lock in that function it may get us out of this potential deadlock. Thanks for reporting. -- Steve > [ 5644.290783] > [ 5644.290783] *** DEADLOCK *** > [ 5644.290783] > [ 5644.290783] 1 lock held by trinity-c17/19105: > [ 5644.290783] #0: (&sig->cred_guard_mutex){+.+.+.}, at: prepare_bprm_creds (fs/exec.c:1165) > [ 5644.290783] > [ 5644.290783] stack backtrace: > [ 5644.290783] CPU: 10 PID: 19105 Comm: trinity-c17 Not tainted 3.14.0-next-20140403-sasha-00019-g7474aa9-dirty #376 > [ 5644.290783] ffffffffb4a1a1e0 ffff88071a7738f8 ffffffffb14bfb2f 0000000000000000 > [ 5644.290783] ffffffffb49a9dd0 ffff88071a773948 ffffffffb14b2527 0000000000000001 > [ 5644.290783] ffff88071a7739d8 ffff88071a773948 ffff8805d98cbcf0 ffff8805d98cbd28 > [ 5644.290783] Call Trace: > [ 5644.290783] dump_stack (lib/dump_stack.c:52) > [ 5644.290783] print_circular_bug (kernel/locking/lockdep.c:1214) > [ 5644.290783] __lock_acquire (kernel/locking/lockdep.c:1840 kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131 kernel/locking/lockdep.c:3182) > [ 5644.290783] ? _raw_spin_unlock_irqrestore (arch/x86/include/asm/paravirt.h:809 include/linux/spinlock_api_smp.h:160 kernel/locking/spinlock.c:191) > [ 5644.290783] ? preempt_count_sub (kernel/sched/core.c:2527) > [ 5644.290783] ? __slab_free (mm/slub.c:2598) > [ 5644.290783] lock_acquire (arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602) > [ 5644.290783] ? trace_array_get (kernel/trace/trace.c:225) > [ 5644.290783] mutex_lock_nested (kernel/locking/mutex.c:486 kernel/locking/mutex.c:587) > [ 5644.290783] ? trace_array_get (kernel/trace/trace.c:225) > [ 5644.290783] ? locks_free_lock (fs/locks.c:244) > [ 5644.290783] ? trace_array_get (kernel/trace/trace.c:225) > [ 5644.290783] ? preempt_count_sub (kernel/sched/core.c:2527) > [ 5644.290783] trace_array_get (kernel/trace/trace.c:225) > [ 5644.290783] tracing_open_generic_tr (kernel/trace/trace.c:3053) > [ 5644.290783] do_dentry_open (fs/open.c:753) > [ 5644.290783] ? tracing_open_pipe (kernel/trace/trace.c:3047) > [ 5644.290783] finish_open (fs/open.c:818) > [ 5644.290783] do_last (fs/namei.c:3040) > [ 5644.290783] ? link_path_walk (fs/namei.c:1473 fs/namei.c:1744) > [ 5644.290783] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) > [ 5644.290783] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2557 kernel/locking/lockdep.c:2599) > [ 5644.290783] path_openat (fs/namei.c:3182) > [ 5644.290783] ? __lock_acquire (kernel/locking/lockdep.c:3189) > [ 5644.290783] do_filp_open (fs/namei.c:3231) > [ 5644.290783] ? put_lock_stats.isra.12 (arch/x86/include/asm/preempt.h:98 kernel/locking/lockdep.c:254) > [ 5644.290783] ? do_execve_common.isra.19 (fs/exec.c:1489) > [ 5644.290783] ? get_parent_ip (kernel/sched/core.c:2472) > [ 5644.290783] do_open_exec (fs/exec.c:766) > [ 5644.290783] do_execve_common.isra.19 (fs/exec.c:1491) > [ 5644.290783] ? do_execve_common.isra.19 (include/linux/spinlock.h:303 fs/exec.c:1258 fs/exec.c:1486) > [ 5644.290783] compat_SyS_execve (fs/exec.c:1627) > [ 5644.290783] ia32_ptregs_common (arch/x86/ia32/ia32entry.S:495) > > > Thanks, > Sasha