linux-kernel - Re: [RFC PATCH 0/2] ipc: do not hold ipc lock more than necessary

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Message-ID: <CANN689HH_bqGSjZ15ftnd_Ogm4YQVJj0_OEQ13nofdEy8WtUmw@mail.gmail.com>
Date:	Sat, 2 Mar 2013 15:08:25 +0800
From:	Michel Lespinasse <walken@...gle.com>
To:	Emmanuel Benisty <benisty.e@...il.com>
Cc:	Davidlohr Bueso <davidlohr.bueso@...com>,
	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Vinod, Chegu" <chegu_vinod@...com>,
	"Low, Jason" <jason.low2@...com>,
	linux-tip-commits@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>, aquini@...hat.com,
	Ingo Molnar <mingo@...nel.org>,
	Larry Woodman <lwoodman@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/2] ipc: do not hold ipc lock more than necessary

On Sat, Mar 2, 2013 at 12:43 PM, Emmanuel Benisty <benisty.e@...il.com> wrote:
> Hi,
>
> On Sat, Mar 2, 2013 at 7:16 AM, Davidlohr Bueso <davidlohr.bueso@...com> wrote:
>> The following set of not-thoroughly-tested patches are based on the
>> discussion of holding the ipc lock unnecessarily, such as for permissions
>> and security checks:
>>
>> https://lkml.org/lkml/2013/2/28/540
>>
>> Patch 0/1: Introduces new functions, analogous to ipc_lock and ipc_lock_check
>> in the ipc utility code, allowing to obtain the ipc object without holding the lock.
>>
>> Patch 0/2: Use the new functions and only acquire the ipc lock when needed.
>
> Not sure how much a work in progress this is but my machine dies
> immediately when I start chromium, crappy mobile phone picture here:
> http://i.imgur.com/S0hfPz3.jpg

We are missing the top of the trace there, so it's hard to be sure -
however, this could well be caused by the if (!out) check (instead of
if (IS_ERR(out)) that I noticed in patch 1/2.

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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