From 5fd3a17ed456637a224cf4ca82b9ad9d005bc8d4 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 4 Mar 2009 00:57:25 -0700 Subject: [PATCH] md: fix deadlock when stopping arrays Resolve a deadlock when stopping redundant arrays, i.e. ones that require a call to sysfs_remove_group when shutdown. The deadlock is summarized below: Thread1 Thread2 ------- ------- read sysfs attribute stop array take mddev lock sysfs_remove_group sysfs_get_active wait for mddev lock wait for active Sysrq-w: -------- mdmon S 00000017 2212 4163 1 f1982ea8 00000046 2dcf6b85 00000017 c0b23100 f2f83ed0 c0b23100 f2f8413c c0b23100 c0b23100 c0b1fb98 f2f8413c 00000000 f2f8413c c0b23100 f2291ecc 00000002 c0b23100 00000000 00000017 f2f83ed0 f1982eac 00000046 c044d9dd Call Trace: [] ? debug_mutex_add_waiter+0x1d/0x58 [] __mutex_lock_common+0x1d9/0x338 [] ? __mutex_lock_common+0x1d9/0x338 [] mutex_lock_interruptible_nested+0x33/0x3a [] ? mddev_lock+0x14/0x16 [] mddev_lock+0x14/0x16 [] md_attr_show+0x2a/0x49 [] sysfs_read_file+0x93/0xf9 mdadm D 00000017 2812 4177 1 f0401d78 00000046 430456f8 00000017 f0401d58 f0401d20 c0b23100 f2da2c4c c0b23100 c0b23100 c0b1fb98 f2da2c4c 0a10fc36 00000000 c0b23100 f0401d70 00000003 c0b23100 00000000 00000017 f2da29e0 00000001 00000002 00000000 Call Trace: [] schedule_timeout+0x1b/0x95 [] ? schedule_timeout+0x1b/0x95 [] ? wait_for_common+0x34/0xdc [] ? trace_hardirqs_on_caller+0x18/0x145 [] ? trace_hardirqs_on+0xb/0xd [] wait_for_common+0xa0/0xdc [] ? default_wake_function+0x0/0x12 [] wait_for_completion+0x17/0x19 [] sysfs_addrm_finish+0x19f/0x1d1 [] sysfs_hash_and_remove+0x42/0x55 [] sysfs_remove_group+0x57/0x86 [] do_md_stop+0x13a/0x499 This has been there for a while, but is easier to trigger now that mdmon is closely watching sysfs. Cc: Reported-by: Jacek Danecki Signed-off-by: Dan Williams --- drivers/md/md.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 03b4cd0a634..a307f87eb90 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -214,12 +214,7 @@ static inline mddev_t *mddev_get(mddev_t *mddev) return mddev; } -static void mddev_delayed_delete(struct work_struct *ws) -{ - mddev_t *mddev = container_of(ws, mddev_t, del_work); - kobject_del(&mddev->kobj); - kobject_put(&mddev->kobj); -} +static void mddev_delayed_delete(struct work_struct *ws); static void mddev_put(mddev_t *mddev) { @@ -3542,6 +3537,21 @@ static struct kobj_type md_ktype = { int mdp_major = 0; +static void mddev_delayed_delete(struct work_struct *ws) +{ + mddev_t *mddev = container_of(ws, mddev_t, del_work); + + if (mddev->private == &md_redundancy_group) { + sysfs_remove_group(&mddev->kobj, &md_redundancy_group); + if (mddev->sysfs_action) + sysfs_put(mddev->sysfs_action); + mddev->sysfs_action = NULL; + mddev->private = NULL; + } + kobject_del(&mddev->kobj); + kobject_put(&mddev->kobj); +} + static int md_alloc(dev_t dev, char *name) { static DEFINE_MUTEX(disks_mutex); @@ -4033,13 +4043,9 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open) mddev->queue->merge_bvec_fn = NULL; mddev->queue->unplug_fn = NULL; mddev->queue->backing_dev_info.congested_fn = NULL; - if (mddev->pers->sync_request) { - sysfs_remove_group(&mddev->kobj, &md_redundancy_group); - if (mddev->sysfs_action) - sysfs_put(mddev->sysfs_action); - mddev->sysfs_action = NULL; - } module_put(mddev->pers->owner); + if (mddev->pers->sync_request) + mddev->private = &md_redundancy_group; mddev->pers = NULL; /* tell userspace to handle 'inactive' */ sysfs_notify_dirent(mddev->sysfs_state); -- 2.39.5