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Date: Mon, 02 Jul 2012 10:06:19 +1000
From: Alexey Kardashevskiy <aik@ozlabs.ru>
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Subject: Re: [Qemu-devel] QEMU question: is eventfd not thread safe?
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Alex Williamson <alex.williamson@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>

On 02/07/12 09:07, Benjamin Herrenschmidt wrote:
>>>> diff --git a/iohandler.c b/iohandler.c
>>>> index 3c74de6..54f4c48 100644
>>>> --- a/iohandler.c
>>>> +++ b/iohandler.c
>>>> @@ -77,6 +77,7 @@ int qemu_set_fd_handler2(int fd,
>>>>          ioh->fd_write = fd_write;
>>>>          ioh->opaque = opaque;
>>>>          ioh->deleted = 0;
>>>> +        kill(getpid(), SIGUSR2);
>>>>      }
>>>>      return 0;
>>>>  }
> 
> That probably wants to be a pthread_kill targetted at the main loop.
> 
>>>> +static void sigusr2_print(int signal)
>>>> +{
>>>> +}
>>>> +
>>>> +static void sigusr2_init(void)
>>>> +{
>>>> +    struct sigaction action;
>>>> +
>>>> +    memset(&action, 0, sizeof(action));
>>>> +    sigfillset(&action.sa_mask);
>>>> +    action.sa_handler = sigusr2_print;
>>>> +    action.sa_flags = 0;
>>>> +    sigaction(SIGUSR2, &action, NULL);
>>>> +}
>>>> +
> 
> Won't that conflict with the business in coroutine-sigaltstack.c ?

The code which touches SIGUSR2 does not compile on power.

> Hrm... looking at it, it looks like it will save/restore the handler,
> so that should be good.
>  
> Still, one might want to wrap that into something, like
> qemu_wake_main_loop();


I already posted another patch with qemu_notify_event() in this mail thread later :)


> 
> Cheers,
> Ben.
> 
>>>>  int main_loop_init(void)
>>>>  {
>>>>      int ret;
>>>>  
>>>> +    sigusr2_init();
>>>> +
>>>>      qemu_mutex_lock_iothread();
>>>>      ret = qemu_signal_init();
>>>>      if (ret) {
>>>> -- 
>>>> 1.7.10
>>
>>
> 
> 


-- 
Alexey