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Date: Tue, 31 May 2011 16:54:20 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: Re: [Qemu-devel] [PATCH] Use SIGIO with caution
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: "qemu-trivial@nongnu.org" <qemu-trivial@nongnu.org>, =?UTF-8?B?QW5kcmU=?= =?UTF-8?B?YXMgRsOkcmJlcg==?= <andreas.faerber@web.de>, Marcelo Tosatti <mtosatti@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>

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 F=C3=A4rber 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 F=C3=A4rber<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 emulati=
on
>>> 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.
>=20
> Is there any reason we still carry multiple timer implementations these=
=20
> days?
>=20
> HPET shouldn't be any better than dynticks.

On any recent kernel, for sure. BTW, the same applies to the RTC timer.

Jan

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