On 2011-01-31 14:17, Avi Kivity wrote:
> On 01/31/2011 01:22 PM, Jan Kiszka wrote:
>> On 2011-01-31 10:52, Avi Kivity wrote:
>>> On 01/27/2011 03:09 PM, Jan Kiszka wrote:
>>>> If there is any pending request that requires us to leave the inner loop
>>>> if main_loop, makes sure we do this as soon as possible by enforcing
>>>> non-blocking IO processing.
>>>>
>>>> At this change, move variable definitions out of the inner loop to
>>>> improve readability.
>>>>
>>>> Signed-off-by: Jan Kiszka<jan.kis...@siemens.com>
>>>> ---
>>>> vl.c | 11 +++++++----
>>>> 1 files changed, 7 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/vl.c b/vl.c
>>>> index 5fad700..2ebc55b 100644
>>>> --- a/vl.c
>>>> +++ b/vl.c
>>>> @@ -1384,18 +1384,21 @@ qemu_irq qemu_system_powerdown;
>>>>
>>>> static void main_loop(void)
>>>> {
>>>> + bool nonblocking = false;
>>>> +#ifdef CONFIG_PROFILER
>>>> + int64_t ti;
>>>> +#endif
>>>> int r;
>>>>
>>>> qemu_main_loop_start();
>>>>
>>>> for (;;) {
>>>> do {
>>>> - bool nonblocking = false;
>>>> -#ifdef CONFIG_PROFILER
>>>> - int64_t ti;
>>>> -#endif
>>>> #ifndef CONFIG_IOTHREAD
>>>> nonblocking = cpu_exec_all();
>>>> + if (!vm_can_run()) {
>>>> + nonblocking = true;
>>>> + }
>>>
>>> Doesn't this cause vmstop to spin? We'll never execute
>>> main_loop_wait(false) if I read the code correctly?
>>>
>>
>> The code path is not changed, we just poll instead of wait in
>> main_loop_wait.
>
> Where do we wait then?
>
>> Also, I didn't get your error scenario yet. Even if we left the loop
>> here, what magic would main_loop_wait do to vmstop processing? The stop
>> request is handled outside the loop, that's why we should leave ASAP.
>
> I'm just missing the alternate place where we sleep. If there's no such
> place, we spin.
>
Probably you are misled by the name of vm_can_run. It should better be
renamed to requests_pending or something like that - iow, it is only
true if some request is pending and not if just the vm is in stop mode.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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