Am 21.11.2017 um 15:59 schrieb Rob Clark:
On Tue, Nov 21, 2017 at 9:38 AM, Chris Wilson chris@chris-wilson.co.uk 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@gmail.com
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.
*/ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, bool wait_all, bool intr,
- greater than zero on success.
@@ -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..
We intentionally switched away from that to be in sync with the wait_event_* interface.
Returning 1 when a function with a zero timeout succeeds is actually quite common in the kernel.
Regards, Christian.
BR, -R
-Chris
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