linux-kernel - Re: [PATCH 1/2] kthread: add a missing memory barrier to kthread

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Message-Id: <200803030850.57615.rusty@rustcorp.com.au>
Date:	Mon, 3 Mar 2008 08:50:56 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Dmitry Adamushko <dmitry.adamushko@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andy Whitcroft <apw@...dowen.org>
Subject: Re: [PATCH 1/2] kthread: add a missing memory barrier to kthread_stop()

On Thursday 21 February 2008 08:36:30 Dmitry Adamushko wrote:
> From: Dmitry Adamushko <dmitry.adamushko@...il.com>
> Subject: kthread: add a missing memory barrier to kthread_stop()
>
> We must ensure that kthread_stop_info.k has been updated before
> kthread's wakeup. This is required to properly support
> the use of kthread_should_stop() in the main loop of kthread.
>
> wake_up_process() doesn't imply a full memory barrier,
> so we add an explicit one.

I always believed that wake_up_process() implies a write barrier.  It's pretty 
common to set something up then wake the intended recipient.

So I think this patch is overkill, but I'm happy to be corrected.

Thanks!
Rusty.
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