linux-kernel - Re: LTTng "TIF_KERNEL

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Message-ID: <20090428164420.GA7337@nowhere>
Date:	Tue, 28 Apr 2009 18:44:21 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizf@...fujitsu.com>, linux-kernel@...r.kernel.org
Subject: Re: LTTng "TIF_KERNEL_TRACE"

On Tue, Apr 28, 2009 at 12:38:25PM -0400, Mathieu Desnoyers wrote:
> No, read-write lock is a "special case" where it does not deadlock if
> you have an interrupt handler taking the read lock over another read
> lock. It's just the write lock that _must absolutely_ disable
> interrupts.


Ah, you're right, I was thinking with spinlock rules in mind :)


> However, the "latency race" scenario I explained above applies here,
> because the write lock disables interrupts and the read locks doesn't.
> 
> Mathieu
> 

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