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pipe: Advance tail pointer inside of wait spinlock in pipe_read() 

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>
This commit is contained in:
David Howells 2019-09-24 16:09:04 +01:00
parent 6718b6f855
commit b667b86734
1 changed files with 7 additions and 1 deletions
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8
fs/pipe.c
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@ -325,9 +325,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (!buf->len) { if (!buf->len) {
pipe_buf_release(pipe, buf); pipe_buf_release(pipe, buf);
spin_lock_irq(&pipe->wait.lock);
tail++; tail++;
pipe->tail = tail; pipe->tail = tail;
do_wakeup = 1; do_wakeup = 0;
wake_up_interruptible_sync_poll_locked(
&pipe->wait, EPOLLOUT | EPOLLWRNORM);
spin_unlock_irq(&pipe->wait.lock);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
} }
total_len -= chars; total_len -= chars;
if (!total_len) if (!total_len)
@ -359,6 +364,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (do_wakeup) { if (do_wakeup) {
wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
do_wakeup = 0;
} }
pipe_wait(pipe); pipe_wait(pipe);
} }