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Subject: Re: [PATCH] Ftrace: irqsoff tracer may cause stack overflow
From: Li Yi <yi.li@analog.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
CC: rostedt@goodmis.org, linux-kernel@vger.kernel.org,
       uclinux-dist-devel@blackfin.uclinux.org
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References: <1262925925.27700.15.camel@adam-desktop>
	 <20100108051847.GB5468@nowhere>
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Date: Fri, 8 Jan 2010 17:13:15 +0800
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On Fri, 2010-01-08 at 06:18 +0100, Frederic Weisbecker wrote:
> On Fri, Jan 08, 2010 at 12:45:25PM +0800, Li Yi wrote:
> > "irqsoff" tracer may cause stack overflow on architectures using
> > asm-generic/atomic.h, due to recursive invoking of, e.g.
> > trace_hardirqs_off().
> > 
> > trace_hardirqs_off() -> start_critical_timing() -> atomic_inc() ->
> > atomic_add_return() -> local_irq_save() -> trace_hardirqs_off()
> > 
> > Signed-off-by: Yi Li <yi.li@analog.com>
> 
> 
> 
> Good catch!
> 
> However, may be we should keep the local_irq_save there
> and have __raw_atomic_* versions only for tracing.
> 
> It's better to keep track of most irq disabled sites.
> 
> Why not something like the following (untested):
Yes. I agree this is better solution.

-Yi