diff options
| -rw-r--r-- | library/std/src/sys/pal/unix/locks/queue_rwlock.rs | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/library/std/src/sys/pal/unix/locks/queue_rwlock.rs b/library/std/src/sys/pal/unix/locks/queue_rwlock.rs index 3a69556165e..76cc28b1285 100644 --- a/library/std/src/sys/pal/unix/locks/queue_rwlock.rs +++ b/library/std/src/sys/pal/unix/locks/queue_rwlock.rs @@ -91,11 +91,12 @@ //! //! Access to the queue is controlled by the `QUEUE_LOCKED` bit, which threads //! try to set both after enqueuing themselves to eagerly add backlinks to the -//! queue and after unlocking the lock to wake the next waiter(s). This is done -//! atomically at the same time as the enqueuing/unlocking operation. The thread -//! releasing the `QUEUE_LOCK` bit will check the state of the lock and wake up -//! waiters as appropriate. This guarantees forward-progress even if the unlocking -//! thread could not acquire the queue lock. +//! queue, which drastically improves performance, and after unlocking the lock +//! to wake the next waiter(s). This is done atomically at the same time as the +//! enqueuing/unlocking operation. The thread releasing the `QUEUE_LOCK` bit +//! will check the state of the lock and wake up waiters as appropriate. This +//! guarantees forward-progress even if the unlocking thread could not acquire +//! the queue lock. //! //! ## Memory orderings //! @@ -358,7 +359,7 @@ impl RwLock { } else { // Otherwise, the tail of the queue is not known. node.tail.set(None); - // Try locking the queue to fully link it. + // Try locking the queue to eagerly add backlinks. next = next.map_addr(|addr| addr | QUEUE_LOCKED); } |