From: Linus Torvalds Date: Fri, 21 Jan 2011 00:21:59 +0000 (-0800) Subject: Fix broken "pipe: use event aware wakeups" optimization X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=28e58ee8ce1f0e69c207f747b7b9054b071e328d;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git Fix broken "pipe: use event aware wakeups" optimization Commit e462c448fdc8 ("pipe: use event aware wakeups") optimized the pipe event wakeup calls to avoid wakeups if the events do not match the requested set. However, the optimization was buggy, in that it didn't actually use the correct sets for the events: when we make room for more data to be written, the pipe poll() routine will return both the POLLOUT _and_ POLLWRNORM bits. Similarly for read. And most critically, when a pipe is released, that will potentially result in POLLHUP|POLLERR (depending on whether it was the last reader or writer), not just the regular POLLIN|POLLOUT. This bug showed itself as a hung gnome-screensaver-dialog process, stuck forever (or at least until it was poked by a signal or by being traced) in a poll() system call. Cc: Davide Libenzi Cc: David S. Miller Cc: Eric Dumazet Cc: Jens Axboe Cc: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/pipe.c b/fs/pipe.c index 89e9e19b1b2e..da42f7db50de 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -441,7 +441,7 @@ redo: break; } if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT); + wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } pipe_wait(pipe); @@ -450,7 +450,7 @@ redo: /* Signal writers asynchronously that there is more room. */ if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT); + wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } if (ret > 0) @@ -612,7 +612,7 @@ redo2: break; } if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, POLLIN); + wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); do_wakeup = 0; } @@ -623,7 +623,7 @@ redo2: out: mutex_unlock(&inode->i_mutex); if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, POLLIN); + wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); } if (ret > 0) @@ -715,7 +715,7 @@ pipe_release(struct inode *inode, int decr, int decw) if (!pipe->readers && !pipe->writers) { free_pipe_info(inode); } else { - wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT); + wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); }