Commit 8446487f authored by David Howells's avatar David Howells
Browse files

pipe: Conditionalise wakeup in pipe_read() 



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: default avatarDavid Howells <dhowells@redhat.com>
parent b667b867

fs/pipe.c

+6 −9
Original line number Diff line number Diff line
@@ -328,10 +328,12 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) 
				spin_lock_irq(&pipe->wait.lock);

				tail++;

				pipe->tail = tail;

				do_wakeup = 0;

				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);

				if (head - (tail - 1) == pipe->max_usage)

					kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);

			}

			total_len -= chars;
@@ -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);

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