linux-kernel - Re: [PATCH] kernel/softirq.c: delete 'while' looping to improve a little performance and beautify code

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Date:	Mon, 10 Jun 2013 16:15:24 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Chen Gang <gang.chen@...anux.com>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Sedat Dilek <sedat.dilek@...il.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/softirq.c: delete 'while' looping to improve a
 little performance and beautify code

On Sun, 9 Jun 2013, Chen Gang wrote:
> After finish the internal 'while', need not test TASKLET_STATE_SCHED
> again, so looping back to outside 'while' is only for set_bit().
> 
> When use 'if' and set_bit() instead of 'while', it will save at least
> one running conditional instruction, and also will be clearer for readers
> (although the binary size will be a little bigger).

And by doing that you break the atomicity of test_and_set_bit. There
is a good reason why this is an atomic operation and why the code is
written as is.
 
> The related patch is "1da177e Linux-2.6.12-rc2"

How is that patch related to the problem?

Thanks

	tglx
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