From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754186AbaJHRwf (ORCPT ); Wed, 8 Oct 2014 13:52:35 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.231]:5254 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754139AbaJHRwd (ORCPT ); Wed, 8 Oct 2014 13:52:33 -0400 Date: Wed, 8 Oct 2014 13:52:16 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Fengguang Wu , Jet Chen , Su Tao , Yuanhan Liu , LKP , linux-kernel@vger.kernel.org Subject: Re: [PATCH] trace: Robustify wait loop Message-ID: <20141008135216.76142204@gandalf.local.home> In-Reply-To: <20141008165110.GA14547@worktop.programming.kicks-ass.net> References: <20141008100613.GA17869@wfg-t540p.sh.intel.com> <20141008104120.GH10832@worktop.programming.kicks-ass.net> <20141008110825.58bdb51d@gandalf.local.home> <20141008154838.GM10832@worktop.programming.kicks-ass.net> <20141008121718.0210c24e@gandalf.local.home> <20141008163657.GN10832@worktop.programming.kicks-ass.net> <20141008165110.GA14547@worktop.programming.kicks-ass.net> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 8 Oct 2014 18:51:10 +0200 Peter Zijlstra wrote: > On Wed, Oct 08, 2014 at 06:36:57PM +0200, Peter Zijlstra wrote: > > > > Right, I'll send the patch. > > I'll see if I can get this in this merge window before I leave to Dusseldorf. BTW, what do you think of this solution? Feel free to ack it if you like it. -- Steve diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index 5ef60499dc8e..593f52b73551 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -1025,6 +1025,12 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr) #endif #ifdef CONFIG_SCHED_TRACER + +struct wakeup_test_data { + struct completion is_ready; + int go; +}; + static int trace_wakeup_test_thread(void *data) { /* Make this a -deadline thread */ @@ -1034,51 +1040,56 @@ static int trace_wakeup_test_thread(void *data) .sched_deadline = 10000000ULL, .sched_period = 10000000ULL }; - struct completion *x = data; + struct wakeup_test_data *x = data; sched_setattr(current, &attr); /* Make it know we have a new prio */ - complete(x); + complete(&x->is_ready); /* now go to sleep and let the test wake us up */ set_current_state(TASK_INTERRUPTIBLE); - schedule(); + while (!x->go) { + schedule(); + set_current_state(TASK_INTERRUPTIBLE); + } - complete(x); + complete(&x->is_ready); + + set_current_state(TASK_INTERRUPTIBLE); /* we are awake, now wait to disappear */ while (!kthread_should_stop()) { - /* - * This will likely be the system top priority - * task, do short sleeps to let others run. - */ - msleep(100); + schedule(); + set_current_state(TASK_INTERRUPTIBLE); } + __set_current_state(TASK_RUNNING); + return 0; } - int trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr) { unsigned long save_max = tr->max_latency; struct task_struct *p; - struct completion is_ready; + struct wakeup_test_data data; unsigned long count; int ret; - init_completion(&is_ready); + memset(&data, 0, sizeof(data)); + + init_completion(&data.is_ready); /* create a -deadline thread */ - p = kthread_run(trace_wakeup_test_thread, &is_ready, "ftrace-test"); + p = kthread_run(trace_wakeup_test_thread, &data, "ftrace-test"); if (IS_ERR(p)) { printk(KERN_CONT "Failed to create ftrace wakeup test thread "); return -1; } /* make sure the thread is running at -deadline policy */ - wait_for_completion(&is_ready); + wait_for_completion(&data.is_ready); /* start the tracing */ ret = tracer_init(trace, tr); @@ -1099,18 +1110,20 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr) msleep(100); } - init_completion(&is_ready); + init_completion(&data.is_ready); + + data.go = 1; + /* memory barrier is in the wake_up_process() */ wake_up_process(p); /* Wait for the task to wake up */ - wait_for_completion(&is_ready); + wait_for_completion(&data.is_ready); /* stop the tracing. */ tracing_stop(); /* check both trace buffers */ ret = trace_test_buffer(&tr->trace_buffer, NULL); - printk("ret = %d\n", ret); if (!ret) ret = trace_test_buffer(&tr->max_buffer, &count);