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Date: Fri, 16 Sep 2011 08:31:26 -0600
From: Eric Blake <eblake@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH RFC] main loop: fix some accesses made in
 sighandler context
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To: lersek@redhat.com, QEMU Developers <qemu-devel@nongnu.org>

> +++ b/cpus.c
> @@ -289,9 +289,16 @@ static void qemu_event_increment(void)
>
>      /* EAGAIN is fine, a read must be pending.  */
>      if (ret < 0 && errno != EAGAIN) {
> -        fprintf(stderr, "qemu_event_increment: write() failed: %s\n",
> -                strerror(errno));
> -        exit (1);
> +        int len;
> +        char buf[128];
> +
> +        /* Don't bother with strerror_[rl]. Make a single attempt to write. */
> +        len = snprintf(buf, sizeof buf,
> +                       "qemu_event_increment: write() failed: %d\n", errno);

snprintf is not async-signal safe (it can malloc, and depending on the 
implementation, tries to grab stdio locks, neither of which is safe).

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org