diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/pipe.c | 31 |
1 files changed, 18 insertions, 13 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index efe93384c61c..bcc2192d33e2 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -276,16 +276,25 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) size_t total_len = iov_iter_count(to); struct file *filp = iocb->ki_filp; struct pipe_inode_info *pipe = filp->private_data; - int do_wakeup; + bool was_full; ssize_t ret; /* Null read succeeds. */ if (unlikely(total_len == 0)) return 0; - do_wakeup = 0; ret = 0; __pipe_lock(pipe); + + /* + * We only wake up writers if the pipe was full when we started + * reading in order to avoid unnecessary wakeups. + * + * But when we do wake up writers, we do so using a sync wakeup + * (WF_SYNC), because we want them to get going and generate more + * data for us. + */ + was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage); for (;;) { unsigned int head = pipe->head; unsigned int tail = pipe->tail; @@ -324,19 +333,11 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) } if (!buf->len) { - bool wake; pipe_buf_release(pipe, buf); spin_lock_irq(&pipe->wait.lock); tail++; pipe->tail = tail; - do_wakeup = 1; - wake = head - (tail - 1) == pipe->max_usage / 2; - if (wake) - wake_up_locked_poll( - &pipe->wait, EPOLLOUT | EPOLLWRNORM); spin_unlock_irq(&pipe->wait.lock); - if (wake) - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } total_len -= chars; if (!total_len) @@ -365,13 +366,17 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) ret = -ERESTARTSYS; break; } + if (was_full) { + wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); + } pipe_wait(pipe); + was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage); } __pipe_unlock(pipe); - /* Signal writers asynchronously that there is more room. */ - if (do_wakeup) { - wake_up_interruptible_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); + if (was_full) { + wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } if (ret > 0) |