linux-kernel - Re: [tip:tracing/urgent] tracing: Allocate the ftrace event profile buffer dynamically

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Message-Id: <1253368035.20020.339.camel@gandalf.stny.rr.com>
Date:	Sat, 19 Sep 2009 09:47:15 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	lizf@...fujitsu.com, peterz@...radead.org, fweisbec@...il.com,
	tglx@...utronix.de, jbaron@...hat.com, mhiramat@...hat.com,
	mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/urgent] tracing: Allocate the ftrace event
 profile buffer dynamically

On Sat, 2009-09-19 at 10:06 +0000, tip-bot for Frederic Weisbecker
wrote:
> Commit-ID:  20ab4425a77a1f34028cc6ce57053c22c184ba5f
> Gitweb:     http://git.kernel.org/tip/20ab4425a77a1f34028cc6ce57053c22c184ba5f
> Author:     Frederic Weisbecker <fweisbec@...il.com>
> AuthorDate: Fri, 18 Sep 2009 06:10:28 +0200
> Committer:  Frederic Weisbecker <fweisbec@...il.com>
> CommitDate: Fri, 18 Sep 2009 07:25:44 +0200
> 
> tracing: Allocate the ftrace event profile buffer dynamically
> 
> Currently the trace event profile buffer is allocated in the stack. But
> this may be too much for the stack, as the events can have large
> statically defined field size and can also grow with dynamic arrays.
> 
> Allocate two per cpu buffer for all profiled events. The first cpu
> buffer is used to host every non-nmi context traces. It is protected
> by disabling the interrupts while writing and committing the trace.
> 
> The second buffer is reserved for nmi. So that there is no race between
> them and the first buffer.
> 
> The whole write/commit section is rcu protected because we release
> these buffers while deactivating the last profiling trace event.
> 
> v2: Move the buffers from trace_event to be global, as pointed by
>     Steven Rostedt.

OK, now I'm confused ;-)

This version looks like the correct one.

-- Steve

> 
> v3: Fix the syscall events to handle the profiling buffer races
>     by disabling interrupts, now that the buffers are globals.
> 
> Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Li Zefan <lizf@...fujitsu.com>
> Cc: Jason Baron <jbaron@...hat.com>
> Cc: Masami Hiramatsu <mhiramat@...hat.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> 


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