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blk-cgroup: Use cond_resched() when destroy blkgs 

mainline inclusion
from mainline-v5.11-rc6
commit 6c635caef4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/ICSIDZ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6c635caef410aa757befbd8857c1eadde5cc22ed

------------------

On !PREEMPT kernel, we can get below softlockup when doing stress
testing with creating and destroying block cgroup repeatly. The
reason is it may take a long time to acquire the queue's lock in
the loop of blkcg_destroy_blkgs(), or the system can accumulate a
huge number of blkgs in pathological cases. We can add a need_resched()
check on each loop and release locks and do cond_resched() if true
to avoid this issue, since the blkcg_destroy_blkgs() is not called
from atomic contexts.

[ 4757.010308] watchdog: BUG: soft lockup - CPU#11 stuck for 94s!
[ 4757.010698] Call trace:
[ 4757.010700]  blkcg_destroy_blkgs+0x68/0x150
[ 4757.010701]  cgwb_release_workfn+0x104/0x158
[ 4757.010702]  process_one_work+0x1bc/0x3f0
[ 4757.010704]  worker_thread+0x164/0x468
[ 4757.010705]  kthread+0x108/0x138

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Conflicts:
	block/blk-cgroup.c
[Due to not merging commit 0d945c1f96 ("block: remove the queue_lock
indirection").]
Signed-off-by: Zheng Qixing <zhengqixing@huawei.com>
This commit is contained in:
Baolin Wang 2025-09-03 11:03:06 +08:00 committed by Zheng Qixing
parent 54968bf231
commit f4038b9336
1 changed files with 13 additions and 5 deletions
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18
block/blk-cgroup.c
View File

@ -1142,6 +1142,8 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
*/
void blkcg_destroy_blkgs(struct blkcg *blkcg)
{
might_sleep();
spin_lock_irq(&blkcg->lock);
while (!hlist_empty(&blkcg->blkg_list)) {
@ -1149,14 +1151,20 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg)
struct blkcg_gq, blkcg_node);
struct request_queue *q = blkg->q;
if (spin_trylock(q->queue_lock)) {
blkg_destroy(blkg);
spin_unlock(q->queue_lock);
} else {
if (need_resched() || !spin_trylock(q->queue_lock)) {
/*
* Given that the system can accumulate a huge number
* of blkgs in pathological cases, check to see if we
* need to rescheduling to avoid softlockup.
*/
spin_unlock_irq(&blkcg->lock);
cpu_relax();
cond_resched();
spin_lock_irq(&blkcg->lock);
continue;
}
blkg_destroy(blkg);
spin_unlock(q->queue_lock);
}
spin_unlock_irq(&blkcg->lock);