Re: [Qemu-devel] [PATCH] Use SIGIO with caution

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/31/2011 10:44 AM, Alexander Graf wrote:
>
> On 31.05.2011, at 16:54, Jan Kiszka wrote:
>
>> On 2011-05-31 16:26, Anthony Liguori wrote:
>>> On 05/31/2011 09:06 AM, Jan Kiszka wrote:
>>>> On 2011-05-31 15:47, Anthony Liguori wrote:
>>>>> On 05/29/2011 04:50 PM, Andreas Färber wrote:
>>>>>> BeOS and Haiku don't define SIGIO. When undefined, it won't arrive
>>>>>> and doesn't need to be blocked.
>>>>>>
>>>>>> Signed-off-by: Andreas Färber<andreas.faerber@web.de>
>>>>>
>>>>> Anything to do with signal masks is never a trivial patch BTW...
>>>>>
>>>>> But I actually think explicit handling of SIGIO is unneeded.  I think
>>>>> this is a hold over from the pre-I/O thread days where we selectively
>>>>> set SIGIO on certain file descriptors to make sure that when an IO fd
>>>>> became readable, we received a signal to break out of the KVM emulation
>>>>> loop.
>>>>>
>>>>> Can the folks on CC confirm/deny?
>>>>>
>>>>> I can't see any use of SIGIO in the current source tree.
>>>>
>>>> At least qemu-timer.c uses SIGIO in HPET mode. That only applies to
>>>> Linux hosts, though.
>>>
>>> Is there any reason we still carry multiple timer implementations these
>>> days?
>>>
>>> HPET shouldn't be any better than dynticks.
>>
>> On any recent kernel, for sure. BTW, the same applies to the RTC timer.
>
> So the obvious change would be to introduce CONFIG_HPET, ifdef the SIGIO handling on that and also ifdef the host hpet handling code on it? That way it's documented well and can preferably even be turned off with --disable-host-hpet during configure time, which we can then slowly turn to the default.

Or just remove hpet and rtc.

Does anyone really object to that?

Regards,

Anthony Liguori

>
> Alex
>
>