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powerpc/qspinlock: Propagate sleepy if previous waiter is preempted

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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>
Tested-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Reviewed-by: "Nysal Jan K.A" <nysal@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231016124305.139923-6-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2023-10-16 22:43:04 +10:00 committed by Michael Ellerman
parent fcf77d4427
commit 1e6d5f7257
1 changed files with 5 additions and 1 deletions
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6
arch/powerpc/lib/qspinlock.c
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@ -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) {