diff options
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 373136f57d7b..3fb574974343 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -3748,7 +3748,15 @@ static __always_inline unsigned int __busy_read_flag(unsigned int id) static __always_inline unsigned int __busy_write_id(unsigned int id) { - return id; + /* The uABI guarantees an active writer is also amongst the read + * engines. This would be true if we accessed the activity tracking + * under the lock, but as we perform the lookup of the object and + * its activity locklessly we can not guarantee that the last_write + * being active implies that we have set the same engine flag from + * last_read - hence we always set both read and write busy for + * last_write. + */ + return id | __busy_read_flag(id); } static __always_inline unsigned int @@ -3857,9 +3865,11 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, args->busy |= busy_check_reader(&obj->last_read[idx]); /* For ABI sanity, we only care that the write engine is in - * the set of read engines. This is ensured by the ordering - * of setting last_read/last_write in i915_vma_move_to_active, - * and then in reverse in retire. + * the set of read engines. This should be ensured by the + * ordering of setting last_read/last_write in + * i915_vma_move_to_active(), and then in reverse in retire. + * However, for good measure, we always report the last_write + * request as a busy read as well as being a busy write. * * We don't care that the set of active read/write engines * may change during construction of the result, as it is |