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blk-cgroup: Use cond_resched() when destroy blkgs
[ Upstream commit 6c635caef4
]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
d1eb418334
commit
513fee2aee
1 changed files with 13 additions and 5 deletions
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@ -1089,6 +1089,8 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
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*/
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void blkcg_destroy_blkgs(struct blkcg *blkcg)
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{
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might_sleep();
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spin_lock_irq(&blkcg->lock);
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while (!hlist_empty(&blkcg->blkg_list)) {
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@ -1096,14 +1098,20 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg)
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struct blkcg_gq, blkcg_node);
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struct request_queue *q = blkg->q;
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if (spin_trylock(&q->queue_lock)) {
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blkg_destroy(blkg);
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spin_unlock(&q->queue_lock);
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} else {
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if (need_resched() || !spin_trylock(&q->queue_lock)) {
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/*
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* Given that the system can accumulate a huge number
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* of blkgs in pathological cases, check to see if we
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* need to rescheduling to avoid softlockup.
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*/
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spin_unlock_irq(&blkcg->lock);
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cpu_relax();
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cond_resched();
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spin_lock_irq(&blkcg->lock);
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continue;
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}
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blkg_destroy(blkg);
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spin_unlock(&q->queue_lock);
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}
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spin_unlock_irq(&blkcg->lock);
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