[PATCH v2 6/6] dm-raid: delay flushing event_work() after reconfig_mutex is released
From: Yu Kuai <hidden>
Date: 2023-11-24 08:03:37
Also in:
lkml
Subsystem:
device-mapper (lvm), software raid (multiple disks) support, the rest · Maintainers:
Alasdair Kergon, Mike Snitzer, Mikulas Patocka, Benjamin Marzinski, Song Liu, Yu Kuai, Linus Torvalds
From: Yu Kuai <redacted>
After commit db5e653d7c9f ("md: delay choosing sync action to
md_start_sync()"), md_start_sync() will hold 'reconfig_mutex', however,
in order to make sure event_work is done, __md_stop() will flush
workqueue with reconfig_mutex grabbed, hence if sync_work is still
pending, deadlock will be triggered.
Fortunately, former pacthes to fix stopping sync_thread already make sure
all sync_work is done already, hence such deadlock is not possible
anymore. However, in order not to cause confusions for people by this
implicit dependency, delay flushing event_work to dm-raid where
'reconfig_mutex' is not held, and add some comments to emphasize that
the workqueue can't be flushed with 'reconfig_mutex'.
Signed-off-by: Yu Kuai <redacted>
---
drivers/md/dm-raid.c | 3 +++
drivers/md/md.c | 11 ++++++++---
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index a4692f8f98ee..51f15c20f621 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c@@ -3317,6 +3317,9 @@ static void raid_dtr(struct dm_target *ti) mddev_lock_nointr(&rs->md); md_stop(&rs->md); mddev_unlock(&rs->md); + + if (work_pending(&rs->md.event_work)) + flush_work(&rs->md.event_work); raid_set_free(rs); }
diff --git a/drivers/md/md.c b/drivers/md/md.c
index fb8a7d1eebee..86efc9c2ae56 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c@@ -82,6 +82,14 @@ static struct module *md_cluster_mod; static DECLARE_WAIT_QUEUE_HEAD(resync_wait); static struct workqueue_struct *md_wq; + +/* + * This workqueue is used for sync_work to register new sync_thread, and for + * del_work to remove rdev, and for event_work that is only set by dm-raid. + * + * Noted that sync_work will grab reconfig_mutex, hence never flush this + * workqueue whith reconfig_mutex grabbed. + */ static struct workqueue_struct *md_misc_wq; struct workqueue_struct *md_bitmap_wq;
@@ -6328,9 +6336,6 @@ static void __md_stop(struct mddev *mddev) struct md_personality *pers = mddev->pers; md_bitmap_destroy(mddev); mddev_detach(mddev); - /* Ensure ->event_work is done */ - if (mddev->event_work.func) - flush_workqueue(md_misc_wq); spin_lock(&mddev->lock); mddev->pers = NULL; spin_unlock(&mddev->lock);
--
2.39.2