This is a note to let you know that I've just added the patch titled
vt: synchronize_rcu() under spinlock is not nice...
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vt-synchronize_rcu-under-spinlock-is-not-nice.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e8cd81693bbbb15db57d3c9aa7dd90eda4842874 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Tue, 26 Mar 2013 20:30:17 -0400
Subject: vt: synchronize_rcu() under spinlock is not nice...
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
commit e8cd81693bbbb15db57d3c9aa7dd90eda4842874 upstream.
vcs_poll_data_free() calls unregister_vt_notifier(), which calls
atomic_notifier_chain_unregister(), which calls synchronize_rcu().
Do it *after* we'd dropped ->f_lock.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/vt/vc_screen.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -93,7 +93,7 @@ vcs_poll_data_free(struct vcs_poll_data
static struct vcs_poll_data *
vcs_poll_data_get(struct file *file)
{
- struct vcs_poll_data *poll = file->private_data;
+ struct vcs_poll_data *poll = file->private_data, *kill = NULL;
if (poll)
return poll;
@@ -122,10 +122,12 @@ vcs_poll_data_get(struct file *file)
file->private_data = poll;
} else {
/* someone else raced ahead of us */
- vcs_poll_data_free(poll);
+ kill = poll;
poll = file->private_data;
}
spin_unlock(&file->f_lock);
+ if (kill)
+ vcs_poll_data_free(kill);
return poll;
}
Patches currently in stable-queue which might be from viro@xxxxxxxxxxxxxxxxxx are
queue-3.4/vt-synchronize_rcu-under-spinlock-is-not-nice.patch
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