Merge v5.4-rc7 into drm-next

We have the i915 security fixes to backmerge, but first
let's clear the decks for other drivers to avoid a bigger
mess.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index 5cff72f18c4a..33ffbf308853 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -106,7 +106,12 @@ retry:
 		was_locked = 1;
 	} else {
 		local_irq_restore(flags);
-		cpu_relax();
+		/*
+		 * Wait for the lock to release before jumping to
+		 * atomic_cmpxchg() in order to mitigate the thundering herd
+		 * problem.
+		 */
+		do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
 		goto retry;
 	}