From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dongsheng Yang <dongsheng081251@gmail.com>,
"yangds.fnst" <yangds.fnst@cn.fujitsu.com>,
linux-kernel@vger.kernel.org, mingo@redhat.com,
bsegall@google.com
Subject: Re: [PATCH] sched: Distinguish sched_wakeup event when wake up a task which did schedule out or not.
Date: Sun, 11 May 2014 14:52:24 -0400 [thread overview]
Message-ID: <20140511145224.00412e59@gandalf.local.home> (raw)
In-Reply-To: <20140511163531.GG30445@twins.programming.kicks-ass.net>
On Sun, 11 May 2014 18:35:31 +0200
Peter Zijlstra <peterz@infradead.org> wrote:
> So if the wait side has already observed cond==false, then without the
> wakeup, which still potentially has ->on_rq == true, it would block.
> Therefore the wakeup is a _real_ wakeup.
>
> We fundamentally cannot know, on the wake side, if the wait side has or
> has not observed cond, and therefore the distinction you're trying to
> make is a false one.
I believe you may be misunderstanding Dongsheng. It has nothing to do
with the wake condition. But the "success" is basically saying, "did I
move the task on to the run queue?". That's a relevant piece of
information that the wake up event isn't currently showing.
Let me ask you this; with Donsheng's patch, will there ever be a
sched_switch event when the wakeup event sees 'false' and the
sched_switch event see the task with a state other than "R"? And if so,
how did the task doing the wakeup event, wake up that task?
-- Steve
next prev parent reply other threads:[~2014-05-11 18:52 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-15 12:32 [PATCH 0/8] perf sched: Add trace event for sched wait Dongsheng Yang
2014-04-15 12:32 ` [PATCH 1/8] sched & trace: Add a trace event for wait Dongsheng Yang
2014-04-15 13:49 ` Peter Zijlstra
2014-04-16 14:23 ` Steven Rostedt
2014-04-15 12:32 ` [PATCH 2/8] sched/wait: Add trace point before add task into wait queue Dongsheng Yang
2014-04-15 12:32 ` [PATCH 3/8] sched/wait: Use __add_wait_queue{_tail}_exclusive() as possible Dongsheng Yang
2014-04-15 13:49 ` Peter Zijlstra
2014-04-16 9:51 ` Dongsheng Yang
2014-04-15 12:32 ` [PATCH 4/8] sched/core: Skip wakeup when task is already running Dongsheng Yang
2014-04-15 13:53 ` Peter Zijlstra
2014-04-16 10:22 ` Dongsheng Yang
2014-04-22 11:56 ` Dongsheng Yang
2014-04-22 13:23 ` Peter Zijlstra
2014-04-22 17:10 ` bsegall
2014-04-22 17:53 ` Steven Rostedt
2014-04-22 18:18 ` Peter Zijlstra
2014-05-05 6:32 ` Dongsheng Yang
2014-05-05 6:34 ` [PATCH] sched: Move the wakeup tracepoint from ttwu_do_wakeup() to ttwu_activate() Dongsheng Yang
2014-05-05 14:00 ` Steven Rostedt
2014-05-06 0:19 ` Dongsheng Yang
2014-05-06 0:26 ` Dongsheng Yang
2014-05-06 2:06 ` Steven Rostedt
2014-05-06 1:29 ` Dongsheng Yang
2014-05-06 1:52 ` [PATCH] sched: Distinguish sched_wakeup event when wake up a task which did schedule out or not Dongsheng Yang
2014-05-09 0:16 ` Dongsheng Yang
2014-05-09 1:27 ` Steven Rostedt
2014-05-10 15:29 ` Peter Zijlstra
[not found] ` <536F90BE.2080806@gmail.com>
2014-05-11 15:24 ` Fwd: " Dongsheng Yang
2014-05-11 16:35 ` Peter Zijlstra
2014-05-11 18:52 ` Steven Rostedt [this message]
2014-05-12 6:47 ` Peter Zijlstra
2014-05-12 8:58 ` Dongsheng Yang
2014-05-12 14:09 ` Steven Rostedt
2014-05-12 15:09 ` Peter Zijlstra
2014-05-12 15:17 ` Steven Rostedt
2014-05-12 15:28 ` Peter Zijlstra
2014-04-15 12:32 ` [PATCH 5/8] perf tools: record and process sched:sched_wait event Dongsheng Yang
2014-04-15 12:32 ` [PATCH 6/8] perf tools: add missing event for perf sched record Dongsheng Yang
2014-04-15 12:32 ` [PATCH 7/8] perf tools: Adapt the TASK_STATE_TO_CHAR_STR to new value in kernel space Dongsheng Yang
2014-04-15 12:32 ` [PATCH 8/8] perf tools: Clarify the output of perf sched map Dongsheng Yang
2014-04-15 13:54 ` [PATCH 0/8] perf sched: Add trace event for sched wait Peter Zijlstra
2014-04-16 10:28 ` Dongsheng Yang
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