linux-kernel - Re: [PATCH] tracing/ftrace: add missing wake-up on some callsites

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Message-ID: <alpine.DEB.2.00.0902231303000.18221@gandalf.stny.rr.com>
Date:	Mon, 23 Feb 2009 13:03:39 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH] tracing/ftrace: add missing wake-up on some callsites


On Mon, 23 Feb 2009, Ingo Molnar wrote:

> 
> * Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > > Which would send a delayed work to wake up?
> > 
> > No, I was thinking that trace_delay_wake_up() would be called 
> > by these dangerous call sites. Then a per_cpu flag could be 
> > set. We could have a trace point in the scheduler code that is 
> > outside holding a runqueue lock, and this trace point would 
> > call a trace function that will clear the per cpu flag, and 
> > then call trace_wake_up().
> 
> No, that's very roundabout and ugly. If we putting a tracepoint 
> there we might as well put real scheduler code there that looks 
> for such a flag. But i'm not convinced we need a flag ...

Just a suggestion. I was trying to keep the tracer from being an overhead. 
But what else would you suggest? Just having the scheduler call 
trace_wakeup?

-- Steve

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