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authorLinus Torvalds <torvalds@linux-foundation.org>2011-01-20 16:21:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-20 16:21:59 -0800
commit28e58ee8ce1f0e69c207f747b7b9054b071e328d (patch)
treeb9191d7e213ad6e8ceb43d45e3306ced085b04f7
parentd7b9935a347ae954be907ea3d5eb4564ff124c53 (diff)
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 <davidel@xmailserver.org> Cc: David S. Miller <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/pipe.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 89e9e19b1b2..da42f7db50d 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);
}