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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <51F9BB8D.6060907@codeaurora.org>
Date:	Wed, 31 Jul 2013 18:36:13 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Timur Tabi <timur@...i.org>,
	Andrew Morton <akpm@...ux-foundation.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 07/31/13 17:20, Timur Tabi wrote:
> 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.

That's encouraging. It looks like you introduced it to use in interrupt
context but then it got shot down[1]? I lost track in all the versions.

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

I read through the v5 discussion and it seems I'm about to walk through
some tall grass on the way to Cerulean City.

Andrew Morton, I choose you! Use your mind-power move to convince
everyone that having a macro for spinning on a register in interrupt
context is a good thing. At least it will be more obvious.

>
>>>> 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
>

[1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2009-May/072521.html

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/