diff options
| -rw-r--r-- | kernel/locking/rwsem.c | 44 |
1 files changed, 34 insertions, 10 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 03cb97a8e4cd..16b532bb5b92 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -375,16 +375,19 @@ rwsem_add_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter) * * Both rwsem_mark_wake() and rwsem_try_write_lock() contain a full 'copy' of * this function. Modify with care. + * + * Return: true if wait_list isn't empty and false otherwise */ -static inline void +static inline bool rwsem_del_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter) { lockdep_assert_held(&sem->wait_lock); list_del(&waiter->list); if (likely(!list_empty(&sem->wait_list))) - return; + return true; atomic_long_andnot(RWSEM_FLAG_HANDOFF | RWSEM_FLAG_WAITERS, &sem->count); + return false; } /* @@ -559,6 +562,33 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, } /* + * Remove a waiter and try to wake up other waiters in the wait queue + * This function is called from the out_nolock path of both the reader and + * writer slowpaths with wait_lock held. It releases the wait_lock and + * optionally wake up waiters before it returns. + */ +static inline void +rwsem_del_wake_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter, + struct wake_q_head *wake_q) + __releases(&sem->wait_lock) +{ + bool first = rwsem_first_waiter(sem) == waiter; + + wake_q_init(wake_q); + + /* + * If the wait_list isn't empty and the waiter to be deleted is + * the first waiter, we wake up the remaining waiters as they may + * be eligible to acquire or spin on the lock. + */ + if (rwsem_del_waiter(sem, waiter) && first) + rwsem_mark_wake(sem, RWSEM_WAKE_ANY, wake_q); + raw_spin_unlock_irq(&sem->wait_lock); + if (!wake_q_empty(wake_q)) + wake_up_q(wake_q); +} + +/* * This function must be called with the sem->wait_lock held to prevent * race conditions between checking the rwsem wait list and setting the * sem->count accordingly. @@ -1050,8 +1080,7 @@ queue: return sem; out_nolock: - rwsem_del_waiter(sem, &waiter); - raw_spin_unlock_irq(&sem->wait_lock); + rwsem_del_wake_waiter(sem, &waiter, &wake_q); __set_current_state(TASK_RUNNING); lockevent_inc(rwsem_rlock_fail); return ERR_PTR(-EINTR); @@ -1095,7 +1124,6 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state) */ raw_spin_unlock_irq(&sem->wait_lock); wake_up_q(&wake_q); - wake_q_init(&wake_q); /* Used again, reinit */ raw_spin_lock_irq(&sem->wait_lock); } } else { @@ -1148,11 +1176,7 @@ trylock_again: out_nolock: __set_current_state(TASK_RUNNING); raw_spin_lock_irq(&sem->wait_lock); - rwsem_del_waiter(sem, &waiter); - if (!list_empty(&sem->wait_list)) - rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q); - raw_spin_unlock_irq(&sem->wait_lock); - wake_up_q(&wake_q); + rwsem_del_wake_waiter(sem, &waiter, &wake_q); lockevent_inc(rwsem_wlock_fail); return ERR_PTR(-EINTR); } |