diff options
| author | NeilBrown <neilb@suse.de> | 2014-04-09 14:33:51 +1000 |
|---|---|---|
| committer | NeilBrown <neilb@suse.de> | 2014-04-09 14:42:34 +1000 |
| commit | e2f23b606b94f28a8febd5aa715df697d80b018e (patch) | |
| tree | d9f21bd649683bedbdadb301b1533c09e13591ba | |
| parent | da1aab3dca9aa88ae34ca392470b8943159e25fe (diff) | |
md: avoid oops on unload if some process is in poll or select.
If md-mod is unloaded while some process is in poll() or select(),
then that process maintains a pointer to md_event_waiters, and when
the try to unlink from that list, they will oops.
The procfs infrastructure ensures that ->poll won't be called after
remove_proc_entry, but doesn't provide a wait_queue_head for us to
use, and the waitqueue code doesn't provide a way to remove all
listeners from a waitqueue.
So we need to:
1/ make sure no further references to md_event_waiters are taken (by
setting md_unloading)
2/ wake up all processes currently waiting, and
3/ wait until all those processes have disconnected from our
wait_queue_head.
Reported-by: "majianpeng" <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
| -rw-r--r-- | drivers/md/md.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c index 3fa2fc0a5dd2..8fda38d23e38 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7165,11 +7165,14 @@ static int md_seq_open(struct inode *inode, struct file *file) return error; } +static int md_unloading; static unsigned int mdstat_poll(struct file *filp, poll_table *wait) { struct seq_file *seq = filp->private_data; int mask; + if (md_unloading) + return POLLIN|POLLRDNORM|POLLERR|POLLPRI;; poll_wait(filp, &md_event_waiters, wait); /* always allow read */ @@ -8655,6 +8658,7 @@ static __exit void md_exit(void) { struct mddev *mddev; struct list_head *tmp; + int delay = 1; blk_unregister_region(MKDEV(MD_MAJOR,0), 1U << MINORBITS); blk_unregister_region(MKDEV(mdp_major,0), 1U << MINORBITS); @@ -8663,7 +8667,19 @@ static __exit void md_exit(void) unregister_blkdev(mdp_major, "mdp"); unregister_reboot_notifier(&md_notifier); unregister_sysctl_table(raid_table_header); + + /* We cannot unload the modules while some process is + * waiting for us in select() or poll() - wake them up + */ + md_unloading = 1; + while (waitqueue_active(&md_event_waiters)) { + /* not safe to leave yet */ + wake_up(&md_event_waiters); + msleep(delay); + delay += delay; + } remove_proc_entry("mdstat", NULL); + for_each_mddev(mddev, tmp) { export_array(mddev); mddev->hold_active = 0; |