[RFC PATCH 04/21] pipe: Advance tail pointer inside of wait spinlock in pipe_read()
From: David Howells <dhowells@redhat.com>
Date: 2019-10-15 21:48:34
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
Advance the pipe ring tail pointer inside of wait spinlock in pipe_read() so that the pipe can be written into with kernel notifications from contexts where pipe->mutex cannot be taken. Signed-off-by: David Howells <dhowells@redhat.com> --- fs/pipe.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 0574277bad18..08af7e7bbea2 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c@@ -324,9 +324,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) if (!buf->len) { pipe_buf_release(pipe, buf); + spin_lock_irq(&pipe->wait.lock); tail++; pipe_commit_read(pipe, tail); - do_wakeup = 1; + do_wakeup = 0; + prelocked_wake_up_interruptible_sync_poll( + &pipe->wait, EPOLLOUT | EPOLLWRNORM); + spin_unlock_irq(&pipe->wait.lock); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } total_len -= chars; if (!total_len)
@@ -358,6 +363,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) 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); }