From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752707AbaEUPaR (ORCPT ); Wed, 21 May 2014 11:30:17 -0400 Received: from casper.infradead.org ([85.118.1.10]:40712 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751658AbaEUPaP (ORCPT ); Wed, 21 May 2014 11:30:15 -0400 Date: Wed, 21 May 2014 17:30:13 +0200 From: Peter Zijlstra To: Dave Jones , Linux Kernel Subject: Re: ye olde task_ctx_sched_out trace. Message-ID: <20140521153013.GG5226@laptop.programming.kicks-ass.net> References: <20140521150613.GA28702@redhat.com> <20140521151655.GG2485@laptop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140521151655.GG2485@laptop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 21, 2014 at 05:16:55PM +0200, Peter Zijlstra wrote: > On Wed, May 21, 2014 at 11:06:13AM -0400, Dave Jones wrote: > > I thought we had this nailed down a while ago, but it still keeps > > popping up... > > > > WARNING: CPU: 3 PID: 32310 at kernel/events/core.c:2384 task_ctx_sched_out+0x6b/0x80() > > CPU: 3 PID: 32310 Comm: trinity-c185 Not tainted 3.15.0-rc5+ #214 > > 0000000000000009 000000003d7dfb5c ffff880019671df8 ffffffff9371a1fd > > 0000000000000000 ffff880019671e30 ffffffff9306d5dd ffff88024d0d6d48 > > ffff88010c4944e8 0000000000000286 ffff880243b82d00 ffff88010c4944e8 > > Call Trace: > > [] dump_stack+0x4e/0x7a > > [] warn_slowpath_common+0x7d/0xa0 > > [] warn_slowpath_null+0x1a/0x20 > > [] task_ctx_sched_out+0x6b/0x80 > > [] perf_event_comm+0xc8/0x220 > > [] ? get_parent_ip+0xd/0x50 > > [] set_task_comm+0x4f/0xc0 > > [] SyS_prctl+0x1d3/0x480 > > [] tracesys+0xdd/0xe2 > > > > There was on perf activity at all going on at the time. > > I had told trinity to do -g vm which excludes all non-VM related syscalls. > > > > What is perf_event_comm doing ? Is that storing some state in case > > I later decide to run perf ? > > So we use perf_event_comm() to trigger start_on_exec, which in turn > pretty much assumes .tsk=current. > > Now some people have advanced set_task_comm() usage far beyond this > point and we can now pretty much call it on random tasks at random times > in order to make 'top' look pretty or similar useless things. > > So I think I should separate this and add perf_event_exec() and leave > perf_event_comm() for just reporting task->comm changes. A little something like so I suppose. --- fs/exec.c | 1 + include/linux/perf_event.h | 1 + kernel/events/core.c | 28 ++++++++++++++++------------ 3 files changed, 18 insertions(+), 12 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 476f3ebf437e..8d51d7ce3dcf 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1111,6 +1111,7 @@ void setup_new_exec(struct linux_binprm * bprm) set_dumpable(current->mm, suid_dumpable); set_task_comm(current, kbasename(bprm->filename)); + perf_event_exec(); /* Set the new mm task size. We have to do that late because it may * depend on TIF_32BIT which is only updated in flush_thread() on diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index af6dcf1d9e47..5975d68a3fe6 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -694,6 +694,7 @@ extern struct perf_guest_info_callbacks *perf_guest_cbs; extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks); extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks); +extern void perf_event_exec(void); extern void perf_event_comm(struct task_struct *tsk); extern void perf_event_fork(struct task_struct *tsk); diff --git a/kernel/events/core.c b/kernel/events/core.c index 7ab734fbaeeb..e46ae0635dca 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2973,6 +2973,22 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx) local_irq_restore(flags); } +void perf_event_exec(void) +{ + struct perf_event_context *ctx; + int ctxn; + + rcu_read_lock(); + for_each_task_context_nr(ctxn) { + ctx = task->perf_event_ctxp[ctxn]; + if (!ctx) + continue; + + perf_event_enable_on_exec(ctx); + } + rcu_read_unlock(); +} + /* * Cross CPU call to read the hardware event */ @@ -5070,18 +5086,6 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event) void perf_event_comm(struct task_struct *task) { struct perf_comm_event comm_event; - struct perf_event_context *ctx; - int ctxn; - - rcu_read_lock(); - for_each_task_context_nr(ctxn) { - ctx = task->perf_event_ctxp[ctxn]; - if (!ctx) - continue; - - perf_event_enable_on_exec(ctx); - } - rcu_read_unlock(); if (!atomic_read(&nr_comm_events)) return;