linux-kernel - Re: [PATCH 2/2] tracing/events/lockdep: move tracepoints within recursive protection

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Message-Id: <1239900469.23397.3128.camel@laptop>
Date:	Thu, 16 Apr 2009 18:47:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 2/2] tracing/events/lockdep: move tracepoints within
 recursive protection

On Thu, 2009-04-16 at 12:15 -0400, Steven Rostedt wrote:
> plain text document attachment
> (0002-tracing-events-lockdep-move-tracepoints-within-recu.patch)
> From: Steven Rostedt <srostedt@...hat.com>
> 
> With the current location of the tracepoints in lockdep, the system
> can hard lockup in minutes when the tracepoints are enabled.
> 
> Moving the tracepoints outside inside the lockdep protection solves
> the issue.

NAK

the idea is to eventually move lockdep on top of the tracepoints. The
tracer should grow to be more robust and handle recursion itself.

Its likely a case of the tracer using a spinlock or mutex in the
tracepoint code. When I did the tracepoints I converted one such to a
raw_spinlock_t in the trace_print code.



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