diff options
Diffstat (limited to 'kernel/locking/rwsem-xadd.c')
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 07713e5..1c0d11e 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) |