From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756779Ab0EaQS1 (ORCPT ); Mon, 31 May 2010 12:18:27 -0400 Received: from casper.infradead.org ([85.118.1.10]:33148 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630Ab0EaQS0 convert rfc822-to-8bit (ORCPT ); Mon, 31 May 2010 12:18:26 -0400 Subject: Re: [PATCH] tracing: Add task activate/deactivate tracepoints From: Peter Zijlstra To: Frederic Weisbecker Cc: Ingo Molnar , LKML , Steven Rostedt In-Reply-To: <20100531144820.GB5157@nowhere> References: <1275056762-13130-1-git-send-regression-fweisbec@gmail.com> <1275059710.27810.9624.camel@twins> <20100531080049.GA435@elte.hu> <1275293544.27810.21478.camel@twins> <1275296099.27810.21622.camel@twins> <20100531143622.GA5157@nowhere> <1275317013.27810.23019.camel@twins> <20100531144820.GB5157@nowhere> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 31 May 2010 18:18:35 +0200 Message-ID: <1275322715.27810.23323.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-05-31 at 16:48 +0200, Frederic Weisbecker wrote: > > Should we maybe cure this and rely on sched_switch() to detect sleeps? > > It seems natural since only the current task can go to sleep, its just > > that the whole preempt state gets a bit iffy. How about something like the below? Steve, is that proper usage of CREATE_TRACE_POINT? --- Subject: sched, trace: Fix sched_switch() prev_state argument From: Peter Zijlstra Date: Mon May 31 18:13:25 CEST 2010 For CONFIG_PREEMPT=y kernels the sched_switch(.prev_state) argument isn't useful because we can get preempted with current->state != TASK_RUNNING without actually getting removed from the runqueue. Cure this by treating all preempted tasks as runnable from the tracer's point of view. Signed-off-by: Peter Zijlstra --- include/trace/events/sched.h | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) Index: linux-2.6/include/trace/events/sched.h =================================================================== --- linux-2.6.orig/include/trace/events/sched.h +++ linux-2.6/include/trace/events/sched.h @@ -115,6 +115,23 @@ DEFINE_EVENT(sched_wakeup_template, sche TP_PROTO(struct task_struct *p, int success), TP_ARGS(p, success)); +#ifdef CREATE_TRACE_POINTS +static inline long __trace_sched_switch_state(struct task_struct *p) +{ + long state = p->state; + +#ifdef CONFIG_PREEMPT + /* + * For all intents and purposes a preempted task is a running task. + */ + if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE) + state = TASK_RUNNING; +#endif + + return state; +} +#endif + /* * Tracepoint for task switches, performed by the scheduler: */ @@ -139,7 +156,7 @@ TRACE_EVENT(sched_switch, memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN); __entry->prev_pid = prev->pid; __entry->prev_prio = prev->prio; - __entry->prev_state = prev->state; + __entry->prev_state = __trace_sched_switch_state(prev); memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN); __entry->next_pid = next->pid; __entry->next_prio = next->prio;