Messages in this thread |  | | Subject | Re: [PATCH] reservation: don't wait when timeout=0 | From | Christian König <> | Date | Tue, 21 Nov 2017 16:49:55 +0100 |
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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. >>> + * 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..
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 > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
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