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Date: Fri, 6 Mar 2009 01:05:55 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Race condition between signal handler and cpu_exec()
Message-ID: <20090306010555.GC13735@shareable.org>
References: <20090305221412.GI17410@hall.aurel32.net>
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To: qemu-devel@nongnu.org

Aurelien Jarno wrote:
> I am currently too tired to find a proper solution (which should only
> use read/write to a variable to keep the operations atomic), I'll look
> at that tomorrow, but patches are welcome in the meanwhile.

The theoretically right thing in C is read/write a "volatile
sig_atomic_t".  The GNU/Linux libc manual has a section "Atomic Data
Access and Signal Handling", where it says you can assume read/writing
an "int" and a pointer are also atomic in this respect on all machines
which matter.

Note that writing to a "char" is not atomic on old Alphas.

-- Jamie