From: Steven Rostedt <rostedt@goodmis.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH 2/4] sched: Use traced preempt count operations to toggle PREEMPT_ACTIVE
Date: Tue, 27 Jan 2015 20:42:39 -0500 [thread overview]
Message-ID: <20150127204239.3d3bc2e4@gandalf.local.home> (raw)
In-Reply-To: <1422404652-29067-3-git-send-email-fweisbec@gmail.com>
On Wed, 28 Jan 2015 01:24:10 +0100
Frederic Weisbecker <fweisbec@gmail.com> wrote:
> d1f74e20b5b064a130cd0743a256c2d3cfe84010 turned PREEMPT_ACTIVE modifiers
> to use raw untraced preempt count operations. Meanwhile this prevents
> from debugging and tracing preemption disabled if we pull that
> responsibility to schedule() callers (see following patches).
>
> Is there anything we can do about that?
>
I'm trying to understand how you solved the recursion issue with
preempt_schedule()?
Here's what happens:
preempt_schedule()
preempt_count_add() -> gets traced by function tracer
function_trace_call()
preempt_disable_notrace()
[...]
preempt_enable_notrace() -> sees NEED_RESCHED set
preempt_schedule()
preempt_count_add() -> gets traced
function_trace_call()
preempt_disable_notrace()
preempt_enable_notrace() -> sees NEED_RESCHED set
[etc etc until BOOM!]
Perhaps if you can find a way to clear NEED_RECHED before disabling
preemption, then it would work. But I don't see that in the patch
series.
-- Steve
next prev parent reply other threads:[~2015-01-28 1:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-28 0:24 [PATCH 0/4] sched: schedule/preempt optimizations and cleanups Frederic Weisbecker
2015-01-28 0:24 ` [PATCH 1/4] sched: Pull resched loop to __schedule() callers Frederic Weisbecker
2015-02-04 14:36 ` [tip:sched/core] " tip-bot for Frederic Weisbecker
2015-01-28 0:24 ` [RFC PATCH 2/4] sched: Use traced preempt count operations to toggle PREEMPT_ACTIVE Frederic Weisbecker
2015-01-28 1:42 ` Steven Rostedt [this message]
2015-01-28 13:59 ` Frederic Weisbecker
2015-01-28 15:04 ` Steven Rostedt
2015-01-28 15:42 ` Peter Zijlstra
2015-02-02 17:22 ` Frederic Weisbecker
2015-01-28 0:24 ` [PATCH 3/4] sched: Pull preemption disablement to __schedule() caller Frederic Weisbecker
2015-01-28 15:50 ` Peter Zijlstra
2015-02-02 17:53 ` Frederic Weisbecker
2015-02-03 10:53 ` Peter Zijlstra
2015-02-04 17:31 ` Frederic Weisbecker
2015-02-04 17:48 ` Peter Zijlstra
2015-01-28 0:24 ` [RFC PATCH 4/4] sched: Account PREEMPT_ACTIVE context as atomic Frederic Weisbecker
2015-01-28 15:46 ` Peter Zijlstra
2015-02-02 17:29 ` Frederic Weisbecker
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