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Date: Sat, 2 Mar 2013 15:08:25 +0800
Message-ID: <CANN689HH_bqGSjZ15ftnd_Ogm4YQVJj0_OEQ13nofdEy8WtUmw@mail.gmail.com>
Subject: Re: [RFC PATCH 0/2] ipc: do not hold ipc lock more than necessary
From: Michel Lespinasse <walken@google.com>
To: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>, Rik van Riel <riel@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        "Vinod, Chegu" <chegu_vinod@hp.com>, "Low, Jason" <jason.low2@hp.com>,
        linux-tip-commits@vger.kernel.org,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>, aquini@redhat.com,
        Ingo Molnar <mingo@kernel.org>, Larry Woodman <lwoodman@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Sat, Mar 2, 2013 at 12:43 PM, Emmanuel Benisty <benisty.e@gmail.com> wrote:
> Hi,
>
> On Sat, Mar 2, 2013 at 7:16 AM, Davidlohr Bueso <davidlohr.bueso@hp.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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