linux-kernel - Re: ipc,sem: sysv semaphore scalability

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Message-ID: <CA+i8gKKNf2105vi93t=KBs5fVRUcaD6BP5hhYE-8cwy2OBAx8w@mail.gmail.com>
Date:	Sat, 30 Mar 2013 12:57:58 +0700
From:	Emmanuel Benisty <benisty.e@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Davidlohr Bueso <davidlohr.bueso@...com>,
	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...riel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	hhuang@...hat.com, "Low, Jason" <jason.low2@...com>,
	Michel Lespinasse <walken@...gle.com>,
	Larry Woodman <lwoodman@...hat.com>,
	"Vinod, Chegu" <chegu_vinod@...com>,
	Peter Hurley <peter@...leysoftware.com>
Subject: Re: ipc,sem: sysv semaphore scalability

On Sat, Mar 30, 2013 at 12:10 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>> Another shot in
>> the dark, I had this weird message when trying to build gcc:
>> semop(2): encountered an error: Identifier removed
>
> This came from the gcc build?

yes, very early in the build process, IIRC this line was repeated a
few times and the build just stalled.

> That's just crazy. No normal app uses sysv semaphores. I have an older
> gcc build environment, and some grepping shows it has some ipc
> semaphore use in the libstdc++ testsuite, and some libmudflap hooks,
> but that should be very very minor.

> I notice that your dmesg says that your kernel is compiled by
> gcc-4.8.1 prerelease. Is there any chance that you could try to
> install a known-stable gcc, like 4.7.2 or something. It's entirely
> possible that it's a kernel bug even if it's triggered by some more
> aggressive compiler optimization or something, but it would be really
> good to try to see if this might be gcc-specific.

I could build a kernel on another machine on which 4.7.2 is installed,
kernel oops'd as well:
http://i.imgur.com/uk6gmq1.jpg

FWIW, I have a few things disabled in my config so here is the one I
used, maybe I'm missing something (but again, everything works
perfectly with your tree):
https://gist.github.com/anonymous/5275566

Lastly, just FTR, I tried Andrew's 3.9-rc4-mm1 and got the same
issues, unsurprisingly I guess.
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