On Tue, Jan 13, 2015 at 11:18:19AM +0100, Maarten Lankhorst wrote: > Op 13-01-15 om 10:22 schreef 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. > I think it would be best to leave timeout=0 returning 0. Not handling it differently gives the same semantics as used by fence_wait_time and wait_event_timeout. > Are there really many cases in which you don't know if timeout = 0 before or not? Yeah I think with this it's more important to be consistent with all the other wait_something primitives the kernel exposes. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
