linux-kernel - Re: [BUG] WARNING: at kernel/trace/ring

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Message-ID: <1268060858.10871.1807.camel@gandalf.stny.rr.com>
Date:	Mon, 08 Mar 2010 10:07:38 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Li Zefan <lizf@...fujitsu.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] WARNING: at kernel/trace/ring_buffer.c:3420

On Mon, 2010-03-08 at 10:03 -0500, Steven Rostedt wrote:

> > ringbuffer resizing and reseting will increase the ->record_disabled
> > and then wait until a rcu_shced grace period passes.
> > 
> > Contrarily, testing ->record_disabled should be at the same
> > preempt disabled critical region as writing into ringbuffer, otherwise
> > it will leave a window break ringbuffer resizing or reseting.
> 
> So the resizing and the resetting need a synchronize_sched() after the
> disabling of the buffers, right?

Looking at the code, the synchronize_sched() is already done in
ring_buffer_resize, and the caller (trace.c:tracing_reset() ) also
disables the ring buffer and calls synchronize_sched().

With that, what other window is still opened (after this fix)?

-- Steve



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