diff options
Diffstat (limited to 'drivers/gpu/drm/i915/i915_gem_request.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_request.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h index 6dd83b172c7a..4e91d4912443 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.h +++ b/drivers/gpu/drm/i915/i915_gem_request.h @@ -51,6 +51,13 @@ struct intel_signal_node { * emission time to be associated with the request for tracking how far ahead * of the GPU the submission is. * + * When modifying this structure be very aware that we perform a lockless + * RCU lookup of it that may race against reallocation of the struct + * from the slab freelist. We intentionally do not zero the structure on + * allocation so that the lookup can use the dangling pointers (and is + * cogniscent that those pointers may be wrong). Instead, everything that + * needs to be initialised must be done so explicitly. + * * The requests are reference counted. */ struct drm_i915_gem_request { @@ -458,6 +465,10 @@ __i915_gem_active_get_rcu(const struct i915_gem_active *active) * just report the active tracker is idle. If the new request is * incomplete, then we acquire a reference on it and check that * it remained the active request. + * + * It is then imperative that we do not zero the request on + * reallocation, so that we can chase the dangling pointers! + * See i915_gem_request_alloc(). */ do { struct drm_i915_gem_request *request; |