Re: [PATCH] drm/i915: fix wait ioctl with negative timeout

[Chia-I Wu <olvaffe@xxxxxxxxx>]

On Sun, Oct 12, 2014 at 1:21 AM, Chia-I Wu <olvaffe@xxxxxxxxx> wrote:

When timeout_ns is negative, it really means to wait indefinitely instead of
returning immediately.  But since userspace can no longer rely on that, I am
not sure if there is any point fixing it.

Note that userspace may use GL_TIMEOUT_IGNORED for timeout_ns to wait indefinitely.  The macro is defined to

#define GL_TIMEOUT_IGNORED                0xFFFFFFFFFFFFFFFFull

Prior to 3.17, the kernel would behave as expected.  But on 3.17, it would return immediately with -ETIME if the bo is busy.

 

Signed-off-by: Chia-I Wu <olvaffe@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ad55b06..3da2d62 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2787,9 +2787,9 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
                 goto out;

        /* Do this after OLR check to make sure we make forward progress polling
-        * on this IOCTL with a timeout <=0 (like busy ioctl)
+        * on this IOCTL with a timeout == 0 (like busy ioctl)
         */
-       if (args->timeout_ns <= 0) {
+       if (args->timeout_ns == 0) {
                ret = -ETIME;
                goto out;
        }
@@ -2798,7 +2798,8 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
        reset_counter = atomic_read(&dev_priv->gpu_error.reset_counter);
        mutex_unlock(&dev->struct_mutex);

-       return __wait_seqno(ring, seqno, reset_counter, true, &args->timeout_ns,
+       return __wait_seqno(ring, seqno, reset_counter, true,
+                           (args->timeout_ns > 0) ? &args->timeout_ns : NULL,
                            file->driver_priv);

 out:
--
2.1.1

--
olv@xxxxxxxxxx

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