From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752623AbaFXHyL (ORCPT ); Tue, 24 Jun 2014 03:54:11 -0400 Received: from relay.parallels.com ([195.214.232.42]:42526 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752164AbaFXHyJ (ORCPT ); Tue, 24 Jun 2014 03:54:09 -0400 Message-ID: <1403596444.3462.28.camel@tkhai> Subject: [PATCH v2 3/3] sched: Rework check_for_tasks() From: Kirill Tkhai To: CC: Peter Zijlstra , Ingo Molnar , , Srikar Dronamraju , "Mike Galbraith" , , Ben Segall , Paul Turner Date: Tue, 24 Jun 2014 11:54:04 +0400 In-Reply-To: <20140624074148.8738.57690.stgit@tkhai> References: <20140624074148.8738.57690.stgit@tkhai> Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 1)Iterate throw all of threads in the system. Check for all threads, not only for group leaders. 2)Check for p->on_rq instead of p->state and cputime. Preempted task in !TASK_RUNNING state OR just created task may be queued, that we want to be reported too. 3)Use read_lock() instead of write_lock(). This function does not change any structures, and read_lock() is enough. Signed-off-by: Kirill Tkhai CC: Konstantin Khorenko CC: Ben Segall CC: Paul Turner CC: Srikar Dronamraju CC: Mike Galbraith CC: Peter Zijlstra CC: Ingo Molnar --- kernel/cpu.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index a343bde..81e2a38 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -274,21 +274,28 @@ void clear_tasks_mm_cpumask(int cpu) rcu_read_unlock(); } -static inline void check_for_tasks(int cpu) +static inline void check_for_tasks(int dead_cpu) { - struct task_struct *p; - cputime_t utime, stime; + struct task_struct *g, *p; - write_lock_irq(&tasklist_lock); - for_each_process(p) { - task_cputime(p, &utime, &stime); - if (task_cpu(p) == cpu && p->state == TASK_RUNNING && - (utime || stime)) - pr_warn("Task %s (pid = %d) is on cpu %d (state = %ld, flags = %x)\n", - p->comm, task_pid_nr(p), cpu, - p->state, p->flags); - } - write_unlock_irq(&tasklist_lock); + read_lock_irq(&tasklist_lock); + do_each_thread(g, p) { + if (!p->on_rq) + continue; + /* + * We do the check with unlocked task_rq(p)->lock. + * Order the reading to do not warn about a task, + * which was running on this cpu in the past, and + * it's just been woken on another cpu. + */ + rmb(); + if (task_cpu(p) != dead_cpu) + continue; + + pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n", + p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags); + } while_each_thread(g, p); + read_unlock_irq(&tasklist_lock); } struct take_cpu_down_param {