From: Thierry Reding treding@nvidia.com
This function is like drm_modeset_lock_all(), but it takes the lock acquisition context as a parameter rather than storing it in the DRM device's mode_config structure.
Implement drm_modeset_{,un}lock_all() in terms of the new function for better code reuse, and add a note to the kerneldoc that new code should use the new functions.
v2: improve kerneldoc v4: rename drm_modeset_lock_all_crtcs() to drm_modeset_lock_all_ctx() and take mode_config's .connection_mutex instead of .mutex lock to avoid lock inversion (Daniel Vetter), use drm_modeset_drop_locks() which is now the equivalent of drm_modeset_unlock_all_ctx() v5: do not take the dev->mode_config.connection_mutex in drm_atomic_legacy_backoff() since drm_modeset_lock_all_ctx() already keeps it, enhance kerneldoc for drm_modeset_lock_all_ctx() (Daniel Vetter)
Signed-off-by: Thierry Reding treding@nvidia.com --- drivers/gpu/drm/drm_atomic.c | 7 +-- drivers/gpu/drm/drm_modeset_lock.c | 89 +++++++++++++++++++++++++------------- include/drm/drm_modeset_lock.h | 4 +- 3 files changed, 63 insertions(+), 37 deletions(-)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index 55b4debad79b..ef5f7663a718 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1188,12 +1188,7 @@ void drm_atomic_legacy_backoff(struct drm_atomic_state *state) retry: drm_modeset_backoff(state->acquire_ctx);
- ret = drm_modeset_lock(&state->dev->mode_config.connection_mutex, - state->acquire_ctx); - if (ret) - goto retry; - ret = drm_modeset_lock_all_crtcs(state->dev, - state->acquire_ctx); + ret = drm_modeset_lock_all_ctx(state->dev, state->acquire_ctx); if (ret) goto retry; } diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c index 6675b1428410..c2f5971146ba 100644 --- a/drivers/gpu/drm/drm_modeset_lock.c +++ b/drivers/gpu/drm/drm_modeset_lock.c @@ -57,11 +57,18 @@
/** * drm_modeset_lock_all - take all modeset locks - * @dev: drm device + * @dev: DRM device * * This function takes all modeset locks, suitable where a more fine-grained - * scheme isn't (yet) implemented. Locks must be dropped with - * drm_modeset_unlock_all. + * scheme isn't (yet) implemented. Locks must be dropped by calling the + * drm_modeset_unlock_all() function. + * + * This function is deprecated. It allocates a lock acquisition context and + * stores it in the DRM device's ->mode_config. This facilitate conversion of + * existing code because it removes the need to manually deal with the + * acquisition context, but it is also brittle because the context is global + * and care must be taken not to nest calls. New code should use the + * drm_modeset_lock_all_ctx() function and pass in the context explicitly. */ void drm_modeset_lock_all(struct drm_device *dev) { @@ -78,39 +85,43 @@ void drm_modeset_lock_all(struct drm_device *dev) drm_modeset_acquire_init(ctx, 0);
retry: - ret = drm_modeset_lock(&config->connection_mutex, ctx); - if (ret) - goto fail; - ret = drm_modeset_lock_all_crtcs(dev, ctx); - if (ret) - goto fail; + ret = drm_modeset_lock_all_ctx(dev, ctx); + if (ret < 0) { + if (ret == -EDEADLK) { + drm_modeset_backoff(ctx); + goto retry; + } + + drm_modeset_acquire_fini(ctx); + kfree(ctx); + return; + }
WARN_ON(config->acquire_ctx);
- /* now we hold the locks, so now that it is safe, stash the - * ctx for drm_modeset_unlock_all(): + /* + * We hold the locks now, so it is safe to stash the acquisition + * context for drm_modeset_unlock_all(). */ config->acquire_ctx = ctx;
drm_warn_on_modeset_not_all_locked(dev); - - return; - -fail: - if (ret == -EDEADLK) { - drm_modeset_backoff(ctx); - goto retry; - } - - kfree(ctx); } EXPORT_SYMBOL(drm_modeset_lock_all);
/** * drm_modeset_unlock_all - drop all modeset locks - * @dev: device + * @dev: DRM device * - * This function drop all modeset locks taken by drm_modeset_lock_all. + * This function drops all modeset locks taken by a previous call to the + * drm_modeset_lock_all() function. + * + * This function is deprecated. It uses the lock acquisition context stored + * in the DRM device's ->mode_config. This facilitates conversion of existing + * code because it removes the need to manually deal with the acquisition + * context, but it is also brittle because the context is global and care must + * be taken not to nest calls. New code should pass the acquisition context + * directly to the drm_modeset_drop_locks() function. */ void drm_modeset_unlock_all(struct drm_device *dev) { @@ -431,14 +442,34 @@ void drm_modeset_unlock(struct drm_modeset_lock *lock) } EXPORT_SYMBOL(drm_modeset_unlock);
-/* In some legacy codepaths it's convenient to just grab all the crtc and plane - * related locks. */ -int drm_modeset_lock_all_crtcs(struct drm_device *dev, - struct drm_modeset_acquire_ctx *ctx) +/** + * drm_modeset_lock_all_ctx - take all modeset locks + * @dev: DRM device + * @ctx: lock acquisition context + * + * This function takes all modeset locks, suitable where a more fine-grained + * scheme isn't (yet) implemented. + * + * Unlike drm_modeset_lock_all(), it doesn't take the dev->mode_config.mutex + * since that lock isn't required for modeset state changes. Callers which + * need to grab that lock too need to do so outside of the acquire context + * @ctx. + * + * Locks acquired with this function should be released by calling the + * drm_modeset_drop_locks() function on @ctx. + * + * Returns: 0 on success or a negative error-code on failure. + */ +int drm_modeset_lock_all_ctx(struct drm_device *dev, + struct drm_modeset_acquire_ctx *ctx) { struct drm_crtc *crtc; struct drm_plane *plane; - int ret = 0; + int ret; + + ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); + if (ret) + return ret;
drm_for_each_crtc(crtc, dev) { ret = drm_modeset_lock(&crtc->mutex, ctx); @@ -454,4 +485,4 @@ int drm_modeset_lock_all_crtcs(struct drm_device *dev,
return 0; } -EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); +EXPORT_SYMBOL(drm_modeset_lock_all_ctx); diff --git a/include/drm/drm_modeset_lock.h b/include/drm/drm_modeset_lock.h index 94938d89347c..c5576fbcb909 100644 --- a/include/drm/drm_modeset_lock.h +++ b/include/drm/drm_modeset_lock.h @@ -138,7 +138,7 @@ void drm_warn_on_modeset_not_all_locked(struct drm_device *dev); struct drm_modeset_acquire_ctx * drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc);
-int drm_modeset_lock_all_crtcs(struct drm_device *dev, - struct drm_modeset_acquire_ctx *ctx); +int drm_modeset_lock_all_ctx(struct drm_device *dev, + struct drm_modeset_acquire_ctx *ctx);
#endif /* DRM_MODESET_LOCK_H_ */