lkml.org 
[lkml]   [2021]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk()
From
Date
在 2021/12/03 18:27, Michal Koutný 写道:
> On Fri, Dec 03, 2021 at 03:50:01PM +0800, "yukuai (C)" <yukuai3@huawei.com> wrote:
>> blkg_destroy() is protected by the queue_lock,so I think queue_lock can
>> protect such concurrent scenario.
>
> blkg_destroy() is not as destroying :-) as actual free, you should
> synchronize against (the queue_lock ensures this for
> pd_free_fn=throtl_pd_free but you may still trip on blkcg after
> blkcg_css_free()).

Hi, Michal

I was thinking that if there are active blkgs, holding queue_lock will
ensure blkcg won't be freed. However, if there are no active blkgs in
the first place, it seems right rcu_read_lock() can prevent this
iteration concurrent with css_release->css_release_work_fn->
css_free_rwork_fn.

By the way, does spin_lock can guarantee this since it disables preempt
like what rcu_read_lock() does?

Thanks,
Kuai

>
> [Actually, I think you should see a warning in your situation if you
> enable CONFIG_PROVE_RCU.]
>
> HTH,
> Michal
>

\
 
 \ /
  Last update: 2021-12-04 09:05    [W:0.041 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site