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Re: [Qemu-discuss] SMP support in the user-mode

From: Soramichi AKIYAMA
Subject: Re: [Qemu-discuss] SMP support in the user-mode
Date: Thu, 25 Aug 2016 08:21:30 +0900

Dear Peter,

thank you very much for the information.

I will look at it more in detail and will report once I'm convinced it is a bug.
(I suspect it's a timing issue since the possibility of the deadlock decreased
when I prolonged the critical section by inserting a meaningless loop inside 



On Wed, 24 Aug 2016 17:16:50 +0100
Peter Maydell <address@hidden> wrote:

> On 24 August 2016 at 07:10, Soramichi AKIYAMA <address@hidden> wrote:
> > I am currently using the user-mode (not system-mode) of QEMU
> > for performance analysis of multi-threaded programs.
> >
> > Although there are several discussions about SMP for the system-mode,
> > I cannot find a thorough documentation about SMP for the user-mode.
> > (I only found this: 
> > http://qemu.weilnetz.de/qemu-tech.html#clone_0028_0029-system-call-and-threads)
> > Is it correctly supported, or in work-in-progress, or in any other state?
> So for a long time supporting multi-threaded guests in QEMU
> usermode wasn't supported at all -- it failed very frequently with
> various crashes. We've fixed some of the most common
> crashes, and so starting from 2.7 it is "supported but buggy".
> That means that mostly it'll work but you will probably find
> bugs, and if you do then we're interested in looking at them
> and trying to fix them.
> thanks
> -- PMM

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