On Thu, 29 Aug 2024 07:58:27 +0530, Nysal Jan K.A. wrote:

If an interrupt occurs in queued_spin_lock_slowpath() after we increment
qnodesp->count and before node->lock is initialized, another CPU might
see stale lock values in get_tail_qnode(). If the stale lock value happens
to match the lock on that CPU, then we write to the "next" pointer of
the wrong qnode. This causes a deadlock as the former CPU, once it becomes
the head of the MCS queue, will spin indefinitely until it's "next" pointer
is set by its successor in the queue.

[...]

Applied to powerpc/fixes.

[1/1] powerpc/qspinlock: Fix deadlock in MCS queue
      https://git.kernel.org/powerpc/c/734ad0af3609464f8f93e00b6c0de1e112f44559

cheers