[PATCH 5/6] powerpc/qspinlock: Propagate sleepy if previous waiter is preempted
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2023-10-16 12:48:17
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
The sleepy (aka lock-owner-is-preempted) condition is propagated down the queue by each waiter. If a waiter becomes preempted, it can no longer propagate sleepy. To allow subsequent waiters to yield to the lock owner, also check the lock owner in this case. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/lib/qspinlock.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c
index 6bb627e90a32..c68c2bd7b853 100644
--- a/arch/powerpc/lib/qspinlock.c
+++ b/arch/powerpc/lib/qspinlock.c@@ -384,7 +384,11 @@ static __always_inline bool yield_to_prev(struct qspinlock *lock, struct qnode * if (!pv_yield_propagate_owner) goto yield_prev; - if (node->sleepy) { + /* + * If the previous waiter was preempted it might not be able to + * propagate sleepy to us, so check the lock in that case too. + */ + if (node->sleepy || vcpu_is_preempted(prev_cpu)) { u32 val = READ_ONCE(lock->val); if (val & _Q_LOCKED_VAL) {
--
2.42.0