linux-kernel - Re: Possible race between PTRACE_SETVFPREGS and PTRACE

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Message-ID: <20160602131539.GA30141@n2100.armlinux.org.uk>
Date:	Thu, 2 Jun 2016 14:15:39 +0100
From:	Russell King - ARM Linux <linux@...linux.org.uk>
To:	Simon Marchi <simon.marchi@...csson.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM?

On Wed, Jun 01, 2016 at 08:54:05AM -0400, Simon Marchi wrote:
> On 16-05-30 05:35 PM, Russell King - ARM Linux wrote:
> > So, the gdb verisons I have here seem to be particularly poor - but with
> > some modifications, I can test out on iMX6 by forcing gdb to do the right
> > thing - by inserting a couple of "mov r0, r0" instructions after the
> > "break_here" label.
> 
> I see that problem too with older versions, bisecting shows it has been fixed
> in commit
> 
>   6e22494e5076 Do not skip prologue for asm (.S) files
> 
> in gdb, which is included in gdb 7.10 and up.
> 
> > With that, on a single CPU, it seems to work correctly every time, but
> > if I bring up a secondary CPU I start seeing the same problems you've
> > reported - which seems to need the following patch to solve.  Please can
> > you check whether this resolves your problem?
> 
> Yes that fixes the problem, the test case succeeds every time.  I have stared
> at those lines in ptrace.c for some time, but couldn't find the problem.  Thanks
> for looking into it!

Hi, can I add a:

Tested-by: Simon Marchi <simon.marchi@...csson.com>

tag to the commit please?

Many thanks.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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