Messages in this thread | | | Subject | Re: [PATCH] blk-cgroup: Use cond_resched() when destroy blkgs | From | Baolin Wang <> | Date | Thu, 28 Jan 2021 09:35:40 +0800 |
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Hi Tejun,
> Hello, Baolin. > > On Tue, Jan 26, 2021 at 09:33:25PM +0800, Baolin Wang wrote: >> 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@linux.alibaba.com> > > * 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.
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