From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>,
"Nysal Jan K . A" <nysal@linux.ibm.com>
Subject: [PATCH 5/6] powerpc/qspinlock: Propagate sleepy if previous waiter is preempted
Date: Mon, 16 Oct 2023 22:43:04 +1000 [thread overview]
Message-ID: <20231016124305.139923-6-npiggin@gmail.com> (raw)
In-Reply-To: <20231016124305.139923-1-npiggin@gmail.com>
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
next prev parent reply other threads:[~2023-10-16 12:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-16 12:42 [PATCH 0/6] powerpc/qspinlock: Fix yield latency bug and other Nicholas Piggin
2023-10-16 12:43 ` [PATCH 1/6] powerpc/qspinlock: Fix stale propagated yield_cpu Nicholas Piggin
2023-10-16 12:43 ` [PATCH 2/6] powerpc/qspinlock: stop queued waiters trying to set lock sleepy Nicholas Piggin
2023-10-20 9:50 ` Nysal Jan K.A.
2023-10-16 12:43 ` [PATCH 3/6] powerpc/qspinlock: propagate owner preemptedness rather than CPU number Nicholas Piggin
2023-10-16 12:43 ` [PATCH 4/6] powerpc/qspinlock: don't propagate the not-sleepy state Nicholas Piggin
2023-10-16 12:43 ` Nicholas Piggin [this message]
2023-10-16 12:43 ` [PATCH 6/6] powerpc/qspinlock: Rename yield_propagate_owner tunable Nicholas Piggin
2023-10-18 7:41 ` [PATCH 0/6] powerpc/qspinlock: Fix yield latency bug and other Shrikanth Hegde
2023-10-20 10:04 ` Nysal Jan K.A.
2023-10-20 12:01 ` (subset) " Michael Ellerman
2023-10-27 9:59 ` Michael Ellerman
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