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-rw-r--r--kernel/locking/rwsem-xadd.c21
1 files changed, 15 insertions, 6 deletions
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 07713e5d9713..1c0d11e8ce34 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -337,21 +337,30 @@ static inline bool owner_running(struct rw_semaphore *sem,
static noinline
bool rwsem_spin_on_owner(struct rw_semaphore *sem, struct task_struct *owner)
{
+ long count;
+
rcu_read_lock();
while (owner_running(sem, owner)) {
- if (need_resched())
- break;
+ /* abort spinning when need_resched */
+ if (need_resched()) {
+ rcu_read_unlock();
+ return false;
+ }
cpu_relax_lowlatency();
}
rcu_read_unlock();
+ if (READ_ONCE(sem->owner))
+ return true; /* new owner, continue spinning */
+
/*
- * We break out the loop above on need_resched() or when the
- * owner changed, which is a sign for heavy contention. Return
- * success only when sem->owner is NULL.
+ * When the owner is not set, the lock could be free or
+ * held by readers. Check the counter to verify the
+ * state.
*/
- return sem->owner == NULL;
+ count = READ_ONCE(sem->count);
+ return (count == 0 || count == RWSEM_WAITING_BIAS);
}
static bool rwsem_optimistic_spin(struct rw_semaphore *sem)