This is a note to let you know that I've just added the patch titled
drm/dp_mst: Handle torn-down topology gracefully in
drm_dp_mst_topology_queue_probe()
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-dp_mst-handle-torn-down-topology-gracefully-in-drm_dp_mst_topology_queue_probe.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 613059875958e7b217b250ed14c3b189f9488421 Mon Sep 17 00:00:00 2001
From: Luca Coelho <[email protected]>
Date: Mon, 22 Jun 2026 17:03:58 +0300
Subject: drm/dp_mst: Handle torn-down topology gracefully in
drm_dp_mst_topology_queue_probe()
From: Luca Coelho <[email protected]>
commit 613059875958e7b217b250ed14c3b189f9488421 upstream.
A hotplug or link-loss event can tear down the MST topology
(setting mgr->mst_state = false and mgr->mst_primary = NULL) concurrently
with a caller invoking drm_dp_mst_topology_queue_probe(). Since the check
is already performed under mgr->lock, the condition is not a programming
error but a valid race -- the topology was valid when the caller decided
to call this function, but was torn down before the lock was acquired.
Replace the drm_WARN_ON() with a graceful early return. This eliminates
spurious kernel warnings and the resulting compositor crashes observed
when connecting/disconnecting DP MST monitors, while keeping the correct
behavior of doing nothing when MST is not active. A drm_dbg_mst() trace
is added so the skipped probe remains observable under MST debug logging.
The existing WARN_ON(mgr->mst_primary) in drm_dp_mst_topology_mgr_set_mst()
already catches the case where the topology is initialized twice, so no
diagnostic coverage is lost.
Fixes: dbaeef363ea5 ("drm/dp_mst: Add a helper to queue a topology probe")
Cc: Imre Deak <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Jonas Emilsson <[email protected]>
Signed-off-by: Luca Coelho <[email protected]>
Link:
https://lore.kernel.org/all/[email protected]
Acked-by: Imre Deak <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Maarten Lankhorst <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/gpu/drm/display/drm_dp_mst_topology.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3743,8 +3743,10 @@ void drm_dp_mst_topology_queue_probe(str
{
mutex_lock(&mgr->lock);
- if (drm_WARN_ON(mgr->dev, !mgr->mst_state || !mgr->mst_primary))
+ if (!mgr->mst_state || !mgr->mst_primary) {
+ drm_dbg_kms(mgr->dev, "queue_probe skipped: topology torn
down\n");
goto out_unlock;
+ }
drm_dp_mst_topology_mgr_invalidate_mstb(mgr->mst_primary);
drm_dp_mst_queue_probe_work(mgr);
Patches currently in stable-queue which might be from [email protected]
are
queue-6.12/drm-dp_mst-handle-torn-down-topology-gracefully-in-drm_dp_mst_topology_queue_probe.patch
