linux-kernel - Re: [RFC 1/1 linux-next] DRIVERS: replace current->state by set_current

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Message-ID: <20150220085621.GL21418@twins.programming.kicks-ass.net>
Date:	Fri, 20 Feb 2015 09:56:21 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Fabian Frederick <fabf@...net.be>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC 1/1 linux-next] DRIVERS: replace current->state by
 set_current_state()

On Thu, Feb 19, 2015 at 09:21:51PM +0100, Fabian Frederick wrote:
> replace remaining direct access to current->state by slower
> helper function in drivers branch.
> Some of them could be optimized later using __set_current_state().

This changelog needs help. Going by this you just make the drivers worse
(slower).

The reason for using set_current_state() is not that its slower, its
because its actually correct; as opposed to direct assignments which are
prone to races and therefore buggy.

Also, since all were direct assignments you can immediately use
__set_current_state() for TASK_RUNNING; code will not be broken more by
that and relying on the barrier for TASK_RUNNING is obscure and rare
anyhow.

So sure, the idea is good, but please, write a coherent changelog to go
with it.
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