lkml.org 
[lkml]   [2017]   [Nov]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] reservation: don't wait when timeout=0
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..

BR,
-R

> -Chris

\
 
 \ /
  Last update: 2017-11-21 16:00    [W:0.049 / U:17.336 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site