Messages in this thread | | | Subject | Re: [PATCH -next v2 9/9] blk-iocost: fix walk_list corruption | From | Yu Kuai <> | Date | Mon, 5 Dec 2022 17:35:07 +0800 |
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Hi, Tejun
在 2022/12/01 4:59, Tejun Heo 写道: > On Wed, Nov 30, 2022 at 09:21:56PM +0800, Li Nan wrote: >> From: Yu Kuai <yukuai3@huawei.com> >> >> Our test report a problem: >> >> ------------[ cut here ]------------ >> list_del corruption. next->prev should be ffff888127e0c4b0, but was ffff888127e090b0 >> WARNING: CPU: 2 PID: 3117789 at lib/list_debug.c:62 __list_del_entry_valid+0x119/0x130 >> RIP: 0010:__list_del_entry_valid+0x119/0x130 >> RIP: 0010:__list_del_entry_valid+0x119/0x130 >> Call Trace: >> <IRQ> >> iocg_flush_stat.isra.0+0x11e/0x230 >> ? ioc_rqos_done+0x230/0x230 >> ? ioc_now+0x14f/0x180 >> ioc_timer_fn+0x569/0x1640 >> >> We haven't reporduced it yet, but we think this is due to parent iocg is >> freed before child iocg, and then in ioc_timer_fn, walk_list is >> corrupted. >> >> 1) Remove child cgroup can concurrent with remove parent cgroup, and >> ioc_pd_free for parent iocg can be called before child iocg. This can be >> fixed by moving the handle of walk_list to ioc_pd_offline, since that >> offline from child is ensured to be called before parent. > > Which you already did in a previous patch, right? > >> 2) ioc_pd_free can be triggered from both removing device and removing >> cgroup, this patch fix the problem by deleting timer before deactivating >> policy, so that free parent iocg first in this case won't matter. > > Okay, so, yeah, css's pin parents but blkg's don't. I think the right thing > to do here is making sure that a child blkg pins its parent (and eventually > ioc).
Sorry about this, actually it's can be ensured that pd_offline from child will be called before parent. Hence just moving he handle of walk_list to ioc_pd_offline can fix this problem thoroughly.
Thanks, Kuai
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