From: Julian Seward <jseward@acm.org>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Race condition between signal handler and cpu_exec()
Date: Fri, 6 Mar 2009 12:49:28 +0100 [thread overview]
Message-ID: <200903061249.29263.jseward@acm.org> (raw)
In-Reply-To: <20090306010555.GC13735@shareable.org>
On Friday 06 March 2009, Jamie Lokier wrote:
> 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".
It looks to me like this requires to atomically test that a bit in a
byte is set, and if so clear it. That would require a lock;cmpxchg
sequence on x86 and lwarx/stwcx on ppc. I wonder if it can be done
with gcc's __sync_bool_compare_and_swap builtin, in order to make
it portable.
J
next prev parent reply other threads:[~2009-03-06 11:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-05 22:14 [Qemu-devel] Race condition between signal handler and cpu_exec() Aurelien Jarno
2009-03-06 1:05 ` Jamie Lokier
2009-03-06 11:49 ` Julian Seward [this message]
2009-03-06 12:30 ` malc
2009-03-06 13:02 ` Jamie Lokier
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