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Date: Tue, 28 Apr 2009 18:44:21 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
       Li Zefan <lizf@cn.fujitsu.com>, linux-kernel@vger.kernel.org
Subject: Re: LTTng "TIF_KERNEL_TRACE"
Message-ID: <20090428164420.GA7337@nowhere>
References: <20090428132037.GA27519@Krystal> <20090428150102.GB26546@elte.hu> <20090428154046.GA32381@Krystal> <20090428163300.GD5978@nowhere> <20090428163825.GA2030@Krystal>
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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
>