[RFC PATCH 07/11] pipe: Conditionalise wakeup in pipe_read() [ver #3]
From: David Howells <dhowells@redhat.com>
Date: 2019-11-01 17:35:18
Also in:
keyrings, linux-block, linux-fsdevel, linux-security-module, linux-usb, lkml
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
Only do a wakeup in pipe_read() if we made space in a completely full buffer. The producer shouldn't be waiting on pipe->wait otherwise. Signed-off-by: David Howells <dhowells@redhat.com> --- fs/pipe.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index ea134f69a292..c16950e36ded 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c@@ -328,11 +328,13 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) spin_lock_irq(&pipe->wait.lock); tail++; pipe->tail = tail; - do_wakeup = 0; - wake_up_interruptible_sync_poll_locked( - &pipe->wait, EPOLLOUT | EPOLLWRNORM); + do_wakeup = 1; + if (head - (tail - 1) == pipe->max_usage) + wake_up_interruptible_sync_poll_locked( + &pipe->wait, EPOLLOUT | EPOLLWRNORM); spin_unlock_irq(&pipe->wait.lock); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); + if (head - (tail - 1) == pipe->max_usage) + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } total_len -= chars; if (!total_len)
@@ -361,11 +363,6 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) ret = -ERESTARTSYS; break; } - if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); - do_wakeup = 0; - } pipe_wait(pipe); } __pipe_unlock(pipe);