The kernel doesn't actually wait indefinately when passed a negative,
timeout, it returns immediately. Document this and suggest using INT64_MAX
for indefinite waits.
Signed-off-by: Kristian Høgsberg <krh@xxxxxxxxxxxxx>
---
We first check if the object is already idle and return 0 if so. Then
we hit this condition:
if (args->timeout_ns <= 0) {
ret = -ETIME;
goto out;
}
and return -ETIME on any timeout value <= 0. I don't know if the ioctl
worked as intended initially and then was broken when this was added, but
either way, there's no point in fixing it. Userspace can use INT64_MAX
for indefinite timeout, which works as well and is simpler trying to
determine whether or not we have a fixed DRM_IOCTL_I915_GEM_WAIT.
intel/intel_bufmgr_gem.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index cf85bb8..d7bfaae 100644
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -1656,12 +1656,14 @@ drm_intel_gem_bo_wait_rendering(drm_intel_bo *bo)
*
* @bo: buffer object to wait for
* @timeout_ns: amount of time to wait in nanoseconds.
- * If value is less than 0, an infinite wait will occur.
+ * If value is less than or equal to 0, return immediately.
*
- * Returns 0 if the wait was successful ie. the last batch referencing the
- * object has completed within the allotted time. Otherwise some negative return
- * value describes the error. Of particular interest is -ETIME when the wait has
- * failed to yield the desired result.
+ * Returns 0 if the wait was successful ie. the last batch referencing
+ * the object has completed within the allotted time. Otherwise some
+ * negative return value describes the error. Of particular interest
+ * is -ETIME when the wait has failed to yield the desired result.
+ * Use a timeout of INT64_MAX to wait indefinitely (well, at least 292
+ * years).
*
* Similar to drm_intel_gem_bo_wait_rendering except a timeout parameter allows
* the operation to give up after a certain amount of time. Another subtle
--
2.1.0
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