These loops in drm_bridge.c iterate over the encoder chain using list_for_each_entry_reverse(), which does not prevent changes to the bridge chain while iterating over it.
Take the encoder chain mutex while iterating to avoid chain changes while iterating. All the "simple" loops are converted. drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_post_disable() are handled by a separate commit. Signed-off-by: Luca Ceresoli <[email protected]> --- Changes in v3: - Lock encoder->bridge_chain_mutex directly, no wrappers Changes in v2: none --- drivers/gpu/drm/drm_bridge.c | 40 ++++++++++++++++++++++------------------ 1 file changed, 22 insertions(+), 18 deletions(-) diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 9b4a075b5361c34c61316c6e52fe55c8928fbc13..eca138eadbc579013db3f588e260489a026baf67 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -710,6 +710,7 @@ void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge, return; encoder = bridge->encoder; + mutex_lock(&encoder->bridge_chain_mutex); list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { if (iter->funcs->atomic_disable) { iter->funcs->atomic_disable(iter, state); @@ -720,6 +721,7 @@ void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge, if (iter == bridge) break; } + mutex_unlock(&encoder->bridge_chain_mutex); } EXPORT_SYMBOL(drm_atomic_bridge_chain_disable); @@ -1224,25 +1226,27 @@ int drm_atomic_bridge_chain_check(struct drm_bridge *bridge, return ret; encoder = bridge->encoder; - list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { - int ret; - - /* - * Bus flags are propagated by default. If a bridge needs to - * tweak the input bus flags for any reason, it should happen - * in its &drm_bridge_funcs.atomic_check() implementation such - * that preceding bridges in the chain can propagate the new - * bus flags. - */ - drm_atomic_bridge_propagate_bus_flags(iter, conn, - crtc_state->state); - - ret = drm_atomic_bridge_check(iter, crtc_state, conn_state); - if (ret) - return ret; + scoped_guard(mutex, &encoder->bridge_chain_mutex) { + list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { + int ret; + + /* + * Bus flags are propagated by default. If a bridge needs to + * tweak the input bus flags for any reason, it should happen + * in its &drm_bridge_funcs.atomic_check() implementation such + * that preceding bridges in the chain can propagate the new + * bus flags. + */ + drm_atomic_bridge_propagate_bus_flags(iter, conn, + crtc_state->state); + + ret = drm_atomic_bridge_check(iter, crtc_state, conn_state); + if (ret) + return ret; - if (iter == bridge) - break; + if (iter == bridge) + break; + } } return 0; -- 2.51.1
