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Re: [Qemu-devel] [PATCH] report that QEMU process was killed by a signal

From: Daniel P. Berrange
Subject: Re: [Qemu-devel] [PATCH] report that QEMU process was killed by a signal
Date: Mon, 14 Mar 2011 13:07:40 +0000
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Mar 14, 2011 at 02:58:55PM +0200, Gleb Natapov wrote:
> Currently when rogue script kills QEMU process (using TERM/INT/HUP
> signal) it looks indistinguishable from system shutdown. Lets report
> that QMEU was killed and leave some clues about the killed identity.

Good idea, but....

> Signed-off-by: Gleb Natapov <address@hidden>
> diff --git a/os-posix.c b/os-posix.c
> index 38c29d1..7e175e8 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -61,8 +61,9 @@ void os_setup_early_signal_handling(void)
>      sigaction(SIGPIPE, &act, NULL);
>  }
> -static void termsig_handler(int signal)
> +static void termsig_handler(int signal, siginfo_t *info, void *c)
>  {
> +    fprintf(stderr, "Got signal %d from pid %d\n", info->si_signo, 
> info->si_pid);
>      qemu_system_shutdown_request();

...fprintf() isn't async signal safe. It could deadlock the process
if it malloc()s while doing the arg formatting & the interrupted
thread was already holding a malloc() lock, or indeed if the stdio
impl itself has internal locks which are held. So this data needs
to be manually output using just write()

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