On 7/3/26 18:31, Natalie Vock wrote:
> TTM is about to switch to drm_exec for locking objects
> in the LRU list. When we're done processing the object, we want to
> unlock it only if the caller doesn't already hold that lock. If
> DRM_EXEC_IGNORE_DUPLICATES is set on the exec object (which callers may
> require for unrelated reasons), we have no way of knowing whether the
> lock is already held.
>
> To remedy this, add a separate helper that forcefully bypasses the
> IGNORE_DUPLICATES flag for only a single locking operation.
>
> Signed-off-by: Natalie Vock <[email protected]>
> ---
> drivers/gpu/drm/drm_exec.c | 52
> ++++++++++++++++++++++++++++++++++------------
> include/drm/drm_exec.h | 2 ++
> 2 files changed, 41 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c
> index 7988f5e7d56a3..91de6b4d29df8 100644
> --- a/drivers/gpu/drm/drm_exec.c
> +++ b/drivers/gpu/drm/drm_exec.c
> @@ -190,18 +190,9 @@ static int drm_exec_lock_contended(struct drm_exec *exec)
> return ret;
> }
>
> -/**
> - * drm_exec_lock_obj - lock a GEM object for use
> - * @exec: the drm_exec object with the state
> - * @obj: the GEM object to lock
> - *
> - * Lock a GEM object for use and grab a reference to it.
> - *
> - * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
> - * already locked (can be suppressed by setting the
> DRM_EXEC_IGNORE_DUPLICATES
> - * flag), -ENOMEM when memory allocation failed and zero for success.
> - */
> -int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
> +static int __drm_exec_lock_obj(struct drm_exec *exec,
> + struct drm_gem_object *obj,
> + bool always_report_duplicates)
Rename the new parameter to ignore_duplicates.
> {
> int ret;
>
> @@ -226,7 +217,7 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct
> drm_gem_object *obj)
> return -EDEADLK;
> }
>
> - if (unlikely(ret == -EALREADY) &&
> + if (unlikely(ret == -EALREADY) && !always_report_duplicates &&
> exec->flags & DRM_EXEC_IGNORE_DUPLICATES)
> return 0;
>
> @@ -243,8 +234,43 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct
> drm_gem_object *obj)
> dma_resv_unlock(obj->resv);
> return ret;
> }
> +
> +/**
> + * drm_exec_lock_obj - lock a GEM object for use
> + * @exec: the drm_exec object with the state
> + * @obj: the GEM object to lock
> + *
> + * Lock a GEM object for use and grab a reference to it.
> + *
> + * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
> + * already locked (can be suppressed by setting the
> DRM_EXEC_IGNORE_DUPLICATES
> + * flag), -ENOMEM when memory allocation failed and zero for success.
> + */
> +int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
> +{
> + return __drm_exec_lock_obj(exec, obj, false);
And then use "exec->flags & DRM_EXEC_IGNORE_DUPLICATES" here.
> +}
> EXPORT_SYMBOL(drm_exec_lock_obj);
>
> +/**
> + * drm_exec_lock_obj_report_dup - lock a GEM object for use, but always
> report duplicates
> + * @exec: the drm_exec object with the state
> + * @obj: the GEM object to lock
> + *
> + * Like drm_exec_lock_obj, lock a GEM object for use and grab a reference to
> it.
> + * Unlike drm_exec_lock_obj, DRM_EXEC_IGNORE_DUPLICATES is ignored and
> duplicates are
> + * always reported.
> + *
> + * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
> + * already locked, -ENOMEM when memory allocation failed and zero for
> success.
> + */
> +int drm_exec_lock_obj_report_dup(struct drm_exec *exec,
> + struct drm_gem_object *obj)
> +{
> + return __drm_exec_lock_obj(exec, obj, false);
BTW That here is buggy, it should have been true.
Apart from that looks good to me,
Christian.
> +}
> +EXPORT_SYMBOL(drm_exec_lock_obj_report_dup);
> +
> /**
> * drm_exec_unlock_obj - unlock a GEM object in this exec context
> * @exec: the drm_exec object with the state
> diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h
> index 8725ba92ff916..ff80dd2b72240 100644
> --- a/include/drm/drm_exec.h
> +++ b/include/drm/drm_exec.h
> @@ -176,6 +176,8 @@ void drm_exec_init(struct drm_exec *exec, u32 flags,
> unsigned nr);
> void drm_exec_fini(struct drm_exec *exec);
> bool drm_exec_cleanup(struct drm_exec *exec);
> int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
> +int drm_exec_lock_obj_report_dup(struct drm_exec *exec,
> + struct drm_gem_object *obj);
> void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
> int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
> unsigned int num_fences);
>
