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Re: [Qemu-ppc] [Qemu-devel] linux-user crashes on clone(2) when run on p

From: Peter Maydell
Subject: Re: [Qemu-ppc] [Qemu-devel] linux-user crashes on clone(2) when run on ppc host
Date: Thu, 18 Jun 2015 08:42:40 +0100

On 17 June 2015 at 22:36, Emilio G. Cota <address@hidden> wrote:
> On Wed, Jun 17, 2015 at 09:58:27 +0100, Peter Maydell wrote:
>> On 17 June 2015 at 01:52, Emilio G. Cota <address@hidden> wrote:
>> > I'm having trouble running a simple multithreaded program on a PowerPC 
>> > host machine.
>> >
>> > The machine I'm using is a ppc VM--I think it's running under KVM (I'm 
>> > using
>> > OVH's RunAbove Power8 service):
>> >   address@hidden:~/qemu$ uname -a
>> >   Linux adsf 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:27:09 UTC 2014 
>> > ppc64le ppc64le ppc64le GNU/Linux
>> >
>> > address@hidden:~/qemu$ ppc64le-linux-user/qemu-ppc64le foo
>> Multithreaded binaries don't work with linux-user; there are a bunch
>> of known race conditions involving data structures we don't correctly
>> lock or make per-thread.
>> This is a long-standing issue; we're hoping we might get to fixing
>> it some time this year.
> I don't think this is a race because it also breaks when
> run on a single core (with taskset -c 0).
> What data structures are you referring to? Are they ppc-specific?

None of the code generation data structures are locked at all --
if two threads try to generate code at the same time they'll
tend to clobber each other.

> On x86 hosts linux-user works reliably with multithreaded apps.

No, it doesn't :-) If any multithreaded app happens to run on
any host it is pure fluke.

-- PMM

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