Re: [PATCH] blk-cgroup: Use cond_resched() when destroy blkgs
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From: Baolin Wang <hidden>
Date: 2021-01-28 01:37:17
Also in:
linux-block, lkml
Hi Tejun,
Hello, Baolin. On Tue, Jan 26, 2021 at 09:33:25PM +0800, Baolin Wang wrote:quoted
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(), thus we can use cond_resched() instead of cpu_relax() 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 Signed-off-by: Baolin Wang <baolin.wang-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>* Can you please add might_sleep() at the top of the function?
Sure.
* Given that the system can accumulate a huge number of blkgs in pathological cases, I wonder whether a better way to go about it is explicitly testing need_resched() on each loop and release locks and do cond_resched() if true?
Yes, sound better to to me and will update in next version. Thanks for your sugestion.