linux-kernel - Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro

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Message-ID: <51F9A9CD.1040804@tabi.org>
Date:	Wed, 31 Jul 2013 19:20:29 -0500
From:	Timur Tabi <timur@...i.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	Arpit Goel <B44344@...escale.com>, linux@....linux.org.uk,
	takata@...ux-m32r.org, philb@....org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	linux390@...ibm.com, David Miller <davem@...emloft.net>,
	Rob Herring <rob.herring@...xeda.com>,
	Arnd Bergmann <arnd@...db.de>,
	Stephen Warren <swarren@...dia.com>, john.stultz@...aro.org,
	jesper.nilsson@...s.com, gregkh@...uxfoundation.org,
	sam@...nborg.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-m32r@...linux-m32r.org, linux-m32r-ja@...linux-m32r.org,
	linux-m68k@...r.kernel.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, mattw@...eaurora.org
Subject: Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture
 independent macro

On 07/31/2013 07:16 PM, Stephen Boyd wrote:
> cpu_relax() is usually just a compiler barrier or an instruction hint to
> the cpu that it should cool down because we're spinning in a tight loop.
> It certainly shouldn't be calling into the  scheduler.

Ah yes, I remember now.  So it does seem that if we can fix the problem
of non-incrementing 'jiffies', then this macro can be used in interrupts.

Of course, that assumes that spinning in interrupt context is a good
idea to begin with.  Maybe we shouldn't be encouraging it?

>> > FYI, you might want to look at the code reviews for spin_event_timeout()
>> > on the linuxppc-dev mailing list, back in March 2009.
>> >
> Sure. Any pointers? Otherwise I'll go digging around the archives.

https://lists.ozlabs.org/pipermail/linuxppc-dev/2009-March/thread.html

-- 
Timur Tabi
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