From: Ingo Molnar <mingo@elte.hu>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
jkenisto@us.ibm.com, a.p.zijlstra@chello.nl, ananth@in.ibm.com,
anton@redhat.com, masami.hiramatsu.pt@hitachi.com,
acme@infradead.org, oleg@redhat.com, tglx@linutronix.de,
Benjamin Herrenschmidt <benh@au1.ibm.com>,
Josh Stone <jistone@redhat.com>,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/uprobes] uprobes/core: Clean up, refactor and improve the code
Date: Mon, 20 Feb 2012 11:51:29 +0100 [thread overview]
Message-ID: <20120220105129.GB24200@elte.hu> (raw)
In-Reply-To: <20120220101337.GE22680@linux.vnet.ibm.com>
* Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> * Ingo Molnar <mingo@elte.hu> [2012-02-20 08:38:23]:
>
> >
> > * Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> >
> > > The volatiles were added to arch/x86/kernel/kprobes.c because
> > > of commit 7115e3fcf45 and 315eb8a2a1b. The volatiles are
> > > required because gcc 4.6 gave a warning about the asm operand
> > > for test_bit. So the same were added to
> > > arch/x86/kernel/uprobes.c.
> >
> > Seems like a GCC bug - a bogus warning - or does it generate bad
> > code as well?
>
> Yes it is a gcc bug and was fixed by Jakub.
> As per Josh, only the first long is output if compiled on the buggy gcc.
That's an important piece of information - the more reason to
document the quirk.
> > In any case, kprobes.c did it correctly, it added the volatile
> > *and a comment*, pointing out that it's a GCC bug. No such
> > warning was added to uprobes.c, making the volatile look
> > entirely spurious.
>
> okay.
Thanks,
Ingo
prev parent reply other threads:[~2012-02-20 10:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-17 9:59 [tip:perf/uprobes] uprobes/core: Clean up, refactor and improve the code tip-bot for Ingo Molnar
2012-02-17 10:49 ` Ingo Molnar
2012-02-20 9:25 ` Srikar Dronamraju
2012-02-20 10:50 ` Ingo Molnar
2012-02-20 6:08 ` Srikar Dronamraju
2012-02-20 7:38 ` Ingo Molnar
2012-02-20 10:13 ` Srikar Dronamraju
2012-02-20 10:51 ` Ingo Molnar [this message]
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