linux-kernel - Re: [PATCH 1/2] tracing/function-return-tracer: Make the function return tracer lockless

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Message-ID: <20081113173451.GY3810@one.firstfloor.org>
Date:	Thu, 13 Nov 2008 18:34:51 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] tracing/function-return-tracer: Make the function return tracer lockless

> So the answer to this is:
> 
>   i = index++;
>   barrier();
>   write to index i (not index);

That was my first thought when I wrote the original email,
but the disadvantage is that barrier() is a big hammer
that flushes everything and can make the code much worse.
That is why I suggested local_add_return() instead.

-Andi

-- 
ak@...ux.intel.com
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