On Fri, Sep 26, 2025 at 05:59:43PM +0200, Luca Ceresoli wrote: > drm_encoder_cleanup() modifies the encoder chain by removing bridges via > drm_bridge_detach(). Protect this whole operation by taking the mutex, so > any users iterating over the chain will not access it during the change. > > Signed-off-by: Luca Ceresoli <[email protected]> > --- > drivers/gpu/drm/drm_encoder.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c > index > 3261f142baea30c516499d23dbf8d0acf5952cd6..3a04bedf9b759acd6826864b7f2cc9b861a8f170 > 100644 > --- a/drivers/gpu/drm/drm_encoder.c > +++ b/drivers/gpu/drm/drm_encoder.c > @@ -195,9 +195,11 @@ void drm_encoder_cleanup(struct drm_encoder *encoder) > * the indices on the drm_encoder after us in the encoder_list. > */ > > + mutex_lock(&encoder->bridge_chain_mutex); > list_for_each_entry_safe(bridge, next, &encoder->bridge_chain, > chain_node) > drm_bridge_detach(bridge); > + mutex_unlock(&encoder->bridge_chain_mutex);
You were claiming that the mutex was to prevent issues with concurrent iteration and removal of the list members. list_for_each_entry_safe() is explicitly made to protect against that. Why do we need both? Maxime
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