[PATCH] reservation: wait only with non-zero timeout specified (v3)

[Christian König]

Am 13.01.2015 um 10:04 schrieb Maarten Lankhorst:
> Op 13-01-15 om 10:36 schreef Jammy Zhou:
>> When the timeout value passed to reservation_object_wait_timeout_rcu
>> is zero, no wait should be done if the fences are not signaled.
>>
>> Return '1' for idle and '0' for busy if the specified timeout is '0'
>> to keep consistent with the case of non-zero timeout.
>>
>> v2: call fence_put if not signaled in the case of timeout==0
>>
>>
> Looks more sane, but where do you need this?

The rational is that we want a single function to call from the driver 
no matter what timeout we have and get a zero if the call timed out and 
a non zero value otherwise.

When we called reservation_object_wait_timeout_rcu with a timeout of 
zero we got a return value of zero as well independent of whether or not 
the fences were signaled. That behavior looked inconsistent and Jammy is 
trying to fix this with this patch.

We could of course do the check in the calling code as well, but to me 
it rather looked like the calling convention of 
reservation_object_wait_timeout_rcu should be thought over one more time.

Either calling it with timeout=0 is invalid and the driver needs to call 
reservation_object_test_signaled_rcu directly instead or we apply this 
patch or something similar to get an useful behavior in the case of 
timeout=0.

Regards,
Christian.

>
> ~Maarten