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Re: [Xen-devel] [PATCH][QEMU] Make active-timers thread-safe

To: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][QEMU] Make active-timers thread-safe
From: Ben Guthro <bguthro@xxxxxxxxxxxxxxx>
Date: Tue, 28 Aug 2007 07:18:59 -0400
Cc: Gary Grebus <ggrebus@xxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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After speaking with the original developer of this patch, it may have been a mistake to port it forward from the 3.1 codebase.

This submission was premature.
We will do some investigation to see if this is still a problem in unstable.


Daniel P. Berrange wrote:
On Mon, Aug 27, 2007 at 02:58:26PM -0400, Ben Guthro wrote:
Protect active_timers[] lists with mutexes so timers can be safely used from different threads.

What code in QEMU is actually still using threads ? There used to be a Xen
specific patch to the IDE layer to perform DMA ops in threads, but that was
removed when xen-unstable synced with QEMU 0.9.0. Not aware of anything
else using threads in the QEMU device model - its pretty dangerous because
QEMU's internal data structures basically all assume single-threaded access.


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