Take the encoder chain mutex while iterating over the encoder chain in drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_post_disable() to ensure the lists won't change while being inspected.
These functions have nested list_for_each_*() loops, which makes them complicated. list_for_each_entry_from() loops could be replaced by drm_for_each_bridge_in_chain_from(), but it would not work in a nested way in its current implementation. Besides, there is no "_reverse" variant of drm_for_each_bridge_in_chain_from(). Keep code simple and readable by explicitly locking around the outer loop. Thankfully there are no break or return points inside the loops, so the change is trivial and readable. Reviewed-by: Maxime Ripard <[email protected]> Signed-off-by: Luca Ceresoli <[email protected]> --- Changes in v3: - Lock encoder->bridge_chain_mutex directly, no wrappers - Improved commit message Changes in v2: - Improved commit message --- drivers/gpu/drm/drm_bridge.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index eca138eadbc579013db3f588e260489a026baf67..76895b0f84d3828034c965b3786c24bfe8b31bfd 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -769,6 +769,7 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge, encoder = bridge->encoder; + mutex_lock(&encoder->bridge_chain_mutex); list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) { limit = NULL; @@ -817,6 +818,7 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge, /* Jump all bridges that we have already post_disabled */ bridge = limit; } + mutex_unlock(&encoder->bridge_chain_mutex); } EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable); @@ -863,6 +865,7 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge, encoder = bridge->encoder; + mutex_lock(&encoder->bridge_chain_mutex); list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { if (iter->pre_enable_prev_first) { next = iter; @@ -905,6 +908,7 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge, if (iter == bridge) break; } + mutex_unlock(&encoder->bridge_chain_mutex); } EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable); -- 2.51.1
