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Date: Mon, 14 May 2012 10:04:44 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH 1.1] Switch SIG_IPI to SIGUSR1
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Michael Tokarev <mjt@tls.msk.ru>, qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>

On 05/09/2012 05:14 PM, Jan Kiszka wrote:
> Use SIGUSR1 unconditionally as SIG_IPI. First, ucontext coroutines tend
> to corrupt RT signal masks due to a 32-on-64-bit Linux kernel bug. And,
> second, there appears to be no advantage in using RT signals for VCPU
> kicking.
>
> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>
> As people prefer to stick with ucontext, this replaces the backend
> switch for i386-linux.
>
> Avi, you once committed the RT signal based SIG_IPI version to
> qemu-kvm. Can you confirm that SIGUSR1 comes with no downside?
>
> This is also stable material.
>
>   main-loop.h |    4 ----
>   1 files changed, 0 insertions(+), 4 deletions(-)
>
> diff --git a/main-loop.h b/main-loop.h
> index c06b8bc..dce1cd9 100644
> --- a/main-loop.h
> +++ b/main-loop.h
> @@ -25,11 +25,7 @@
>   #ifndef QEMU_MAIN_LOOP_H
>   #define QEMU_MAIN_LOOP_H 1
>
> -#ifdef SIGRTMIN
> -#define SIG_IPI (SIGRTMIN+4)
> -#else
>   #define SIG_IPI SIGUSR1
> -#endif
>
>   /**
>    * qemu_init_main_loop: Set up the process so that it can run the main loop.