On Tue, Nov 21, 2017 at 9:38 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > Quoting Rob Clark (2017-11-21 14:08:46) >> If we are testing if a reservation object's fences have been >> signaled with timeout=0 (non-blocking), we need to pass 0 for >> timeout to dma_fence_wait_timeout(). >> >> Plus bonus spelling correction. >> >> Signed-off-by: Rob Clark <robdclark@xxxxxxxxx> >> --- >> drivers/dma-buf/reservation.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c >> index dec3a815455d..71f51140a9ad 100644 >> --- a/drivers/dma-buf/reservation.c >> +++ b/drivers/dma-buf/reservation.c >> @@ -420,7 +420,7 @@ EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu); >> * >> * RETURNS >> * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or >> - * greater than zer on success. >> + * greater than zero on success. >> */ >> long reservation_object_wait_timeout_rcu(struct reservation_object *obj, >> bool wait_all, bool intr, >> @@ -483,7 +483,14 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, >> goto retry; >> } >> >> - ret = dma_fence_wait_timeout(fence, intr, ret); >> + /* >> + * Note that dma_fence_wait_timeout() will return 1 if >> + * the fence is already signaled, so in the wait_all >> + * case when we go through the retry loop again, ret >> + * will be greater than 0 and we don't want this to >> + * cause _wait_timeout() to block >> + */ >> + ret = dma_fence_wait_timeout(fence, intr, timeout ? ret : 0); > > One should ask if we should just fix the interface to stop returning > incorrect results (stop "correcting" a completion with 0 jiffies remaining > as 1). A timeout can be distinguished by -ETIME (or your pick of errno). perhaps -EBUSY, if we go that route (although maybe it should be a follow-on patch, this one is suitable for backport to stable/lts if one should so choose..) I think current approach was chosen to match schedule_timeout() and other such functions that take a timeout in jiffies. Not making a judgement on whether that is a good or bad reason.. BR, -R > -Chris
