drm/i915: fix wait ioctl with negative timeout

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.

Signed-off-by Chia-I Wu <[email protected]>

---
 drivers/gpu/drm/i915/i915_gem.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

drivers/gpu/drm/i915/i915_gem.c +0 -0

index ad55b06..3da2d62 100644
@@ -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

drivers/gpu/drm/i915/i915_gem.c +4 -3

-        * 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

Quoted 6 lines · Chia-I Wu

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.