diff options
Diffstat (limited to 'kernel/locking/rwsem.c')
| -rw-r--r-- | kernel/locking/rwsem.c | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 37524a47f002..bd0f0d05724c 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -666,7 +666,11 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem, preempt_disable(); rcu_read_lock(); owner = rwsem_owner_flags(sem, &flags); - if ((flags & nonspinnable) || (owner && !owner_on_cpu(owner))) + /* + * Don't check the read-owner as the entry may be stale. + */ + if ((flags & nonspinnable) || + (owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner))) ret = false; rcu_read_unlock(); preempt_enable(); @@ -1000,6 +1004,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state) atomic_long_add(-RWSEM_READER_BIAS, &sem->count); adjustment = 0; if (rwsem_optimistic_spin(sem, false)) { + /* rwsem_optimistic_spin() implies ACQUIRE on success */ /* * Wake up other readers in the wait list if the front * waiter is a reader. @@ -1014,6 +1019,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state) } return sem; } else if (rwsem_reader_phase_trylock(sem, waiter.last_rowner)) { + /* rwsem_reader_phase_trylock() implies ACQUIRE on success */ return sem; } @@ -1032,6 +1038,8 @@ queue: */ if (adjustment && !(atomic_long_read(&sem->count) & (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) { + /* Provide lock ACQUIRE */ + smp_acquire__after_ctrl_dep(); raw_spin_unlock_irq(&sem->wait_lock); rwsem_set_reader_owned(sem); lockevent_inc(rwsem_rlock_fast); @@ -1065,15 +1073,18 @@ queue: wake_up_q(&wake_q); /* wait to be given the lock */ - while (true) { + for (;;) { set_current_state(state); - if (!waiter.task) + if (!smp_load_acquire(&waiter.task)) { + /* Matches rwsem_mark_wake()'s smp_store_release(). */ break; + } if (signal_pending_state(state, current)) { raw_spin_lock_irq(&sem->wait_lock); if (waiter.task) goto out_nolock; raw_spin_unlock_irq(&sem->wait_lock); + /* Ordered by sem->wait_lock against rwsem_mark_wake(). */ break; } schedule(); @@ -1083,6 +1094,7 @@ queue: __set_current_state(TASK_RUNNING); lockevent_inc(rwsem_rlock); return sem; + out_nolock: list_del(&waiter.list); if (list_empty(&sem->wait_list)) { @@ -1123,8 +1135,10 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state) /* do optimistic spinning and steal lock if possible */ if (rwsem_can_spin_on_owner(sem, RWSEM_WR_NONSPINNABLE) && - rwsem_optimistic_spin(sem, true)) + rwsem_optimistic_spin(sem, true)) { + /* rwsem_optimistic_spin() implies ACQUIRE on success */ return sem; + } /* * Disable reader optimistic spinning for this rwsem after @@ -1184,9 +1198,11 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state) wait: /* wait until we successfully acquire the lock */ set_current_state(state); - while (true) { - if (rwsem_try_write_lock(sem, wstate)) + for (;;) { + if (rwsem_try_write_lock(sem, wstate)) { + /* rwsem_try_write_lock() implies ACQUIRE on success */ break; + } raw_spin_unlock_irq(&sem->wait_lock); |