Re: [Qemu-devel] [PATCH v6 5/7] qemu-coroutine-sleep: introduce qemu_co_sleep_wake

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

07.06.2019 16:02, Kevin Wolf wrote:
> Am 07.06.2019 um 13:18 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> 07.06.2019 10:57, Kevin Wolf wrote:
>>> Am 11.04.2019 um 19:27 hat Vladimir Sementsov-Ogievskiy geschrieben:
>>>> Introduce a function to gracefully wake-up a coroutine, sleeping in
>>>> qemu_co_sleep_ns() sleep.
>>>>
>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>
>>> You can simply reenter the coroutine while it has yielded in
>>> qemu_co_sleep_ns(). This is supported.
>>
>> No it doesn't. qemu_aio_coroutine_enter checks for scheduled field,
>> and aborts if it is set.
> 
> Ah, yes, it has been broken since commit
> 
> I actually tried to fix it once, but it turned out more complicated and
> I think we found a different solution for the problem at hand:
> 
>      Subject: [PATCH for-2.11 0/4] Fix qemu-iotests failures
>      Message-Id: <20171128154350.21504-1-kwolf@redhat.com>
> 
> In this case, I guess your approach with a new function to interrupt
> qemu_co_sleep_ns() is okay.
> 
> Do we need to timer_del() when taking the shortcut? We don't necessarily
> reenter the coroutine immediately, but might only be scheduling it. In
> this case, the timer could fire before qemu_co_sleep_ns() has run and
> schedule the coroutine a second time (ignoring co->scheduled again -
> maybe we should actually not do that in the timer callback path, but
> instead let it run into the assertion because it would be a bug for the
> timer callback to end up in this situation).
> 

Ok, thanks, will try to improve it


-- 
Best regards,
Vladimir