[src/trunk]: src/sys/external/bsd/drm2/linux drm/dma-fence: Fix zero timeout ...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/a9d0f2325c8a
branches:  trunk
changeset: 1028569:a9d0f2325c8a
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 11:20:49 2021 +0000

description:
drm/dma-fence: Fix zero timeout semantics in dma_fence_default_wait.

diffstat:

 sys/external/bsd/drm2/linux/linux_dma_fence.c |  29 +++++++++++++++-----------
 1 files changed, 17 insertions(+), 12 deletions(-)

diffs (68 lines):

diff -r 0f0f1fa1e132 -r a9d0f2325c8a sys/external/bsd/drm2/linux/linux_dma_fence.c
--- a/sys/external/bsd/drm2/linux/linux_dma_fence.c     Sun Dec 19 11:20:41 2021 +0000
+++ b/sys/external/bsd/drm2/linux/linux_dma_fence.c     Sun Dec 19 11:20:49 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_dma_fence.c,v 1.15 2021/12/19 11:09:17 riastradh Exp $   */
+/*     $NetBSD: linux_dma_fence.c,v 1.16 2021/12/19 11:20:49 riastradh Exp $   */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.15 2021/12/19 11:09:17 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.16 2021/12/19 11:20:49 riastradh Exp $");
 
 #include <sys/atomic.h>
 #include <sys/condvar.h>
@@ -782,10 +782,11 @@
  *
  *     Default implementation of fence wait callback using a condition
  *     variable.  If the fence is already signalled, return timeout,
- *     or 1 if no timeout.  If the enable signalling callback hasn't
- *     been called, call it, and if it fails, act as if the fence had
- *     been signalled.  Otherwise, wait on the internal condvar.  If
- *     timeout is MAX_SCHEDULE_TIMEOUT, treat it as no timeout.
+ *     or 1 if timeout is zero meaning poll.  If the enable signalling
+ *     callback hasn't been called, call it, and if it fails, act as
+ *     if the fence had been signalled.  Otherwise, wait on the
+ *     internal condvar.  If timeout is MAX_SCHEDULE_TIMEOUT, wait
+ *     indefinitely.
  */
 long
 dma_fence_default_wait(struct dma_fence *fence, bool intr, long timeout)
@@ -800,15 +801,20 @@
 
        /* Optimistically try to skip the lock if it's already signalled.  */
        if (fence->flags & (1u << DMA_FENCE_FLAG_SIGNALED_BIT))
-               return (timeout < MAX_SCHEDULE_TIMEOUT ? timeout : 1);
+               return (timeout ? timeout : 1);
 
        /* Acquire the lock.  */
        spin_lock(fence->lock);
 
-       /* Ensure signalling is enabled, or fail if we can't.  */
-       ret = dma_fence_ensure_signal_enabled(fence);
-       if (ret)
-               goto out;
+       /* Ensure signalling is enabled, or stop if already completed.  */
+       if (dma_fence_ensure_signal_enabled(fence) != 0)
+               return (timeout ? timeout : 1);
+
+       /* If merely polling, stop here.  */
+       if (timeout == 0) {
+               spin_unlock(fence->lock);
+               return 0;
+       }
 
        /* Find out what our deadline is so we can handle spurious wakeup.  */
        if (timeout < MAX_SCHEDULE_TIMEOUT) {
@@ -854,7 +860,6 @@
                }
        }
 
-out:
        /* All done.  Release the lock.  */
        spin_unlock(fence->lock);