From: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH 2/2] cpuset: remove redundant checks in file write functions
Date: Wed, 14 Aug 2013 10:01:32 +0800 [thread overview]
Message-ID: <520AE4FC.5090702@huawei.com> (raw)
In-Reply-To: <20130813150549.GF26596-9pTldWuhBndy/B6EtB590w@public.gmane.org>
On 2013/8/13 23:05, Tejun Heo wrote:
> On Tue, Aug 13, 2013 at 09:17:53AM +0800, Li Zefan wrote:
>> Now cgroup core gets a reference to the css when a cgroup file is
>> opened(), and the reference is dropped at file release. so it's
>> guaranteed the cpuset is online during the write function.
>
> Hmmm... it doesn't really guarantee that as css's can be offlined with
> residual css refcnts, os the css may well be offlined by the time it
> reaches the rw functions. What's guaranteed is that their refcnts
> wouldn't be zero.
Oh, right.
But most controllers don't check this in those read/write functions.
It shoudn't do any harm not checking online/offline status.
> Eventually we need to implement proper sever
> semantics (probably by replacing the custom fs implementation with
> sysfs) but right now controllers still need to deal with offline
> css's.
>
> Thanks.
>
WARNING: multiple messages have this Message-ID (diff)
From: Li Zefan <lizefan@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH 2/2] cpuset: remove redundant checks in file write functions
Date: Wed, 14 Aug 2013 10:01:32 +0800 [thread overview]
Message-ID: <520AE4FC.5090702@huawei.com> (raw)
In-Reply-To: <20130813150549.GF26596@mtj.dyndns.org>
On 2013/8/13 23:05, Tejun Heo wrote:
> On Tue, Aug 13, 2013 at 09:17:53AM +0800, Li Zefan wrote:
>> Now cgroup core gets a reference to the css when a cgroup file is
>> opened(), and the reference is dropped at file release. so it's
>> guaranteed the cpuset is online during the write function.
>
> Hmmm... it doesn't really guarantee that as css's can be offlined with
> residual css refcnts, os the css may well be offlined by the time it
> reaches the rw functions. What's guaranteed is that their refcnts
> wouldn't be zero.
Oh, right.
But most controllers don't check this in those read/write functions.
It shoudn't do any harm not checking online/offline status.
> Eventually we need to implement proper sever
> semantics (probably by replacing the custom fs implementation with
> sysfs) but right now controllers still need to deal with offline
> css's.
>
> Thanks.
>
next prev parent reply other threads:[~2013-08-14 2:01 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-13 1:17 [PATCH 1/2] cpuset: remove an unncessary forward declaration Li Zefan
2013-08-13 1:17 ` Li Zefan
[not found] ` <5209892D.8070502-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-08-13 1:17 ` [PATCH 2/2] cpuset: remove redundant checks in file write functions Li Zefan
2013-08-13 1:17 ` Li Zefan
[not found] ` <52098941.4070600-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-08-13 2:07 ` Li Zefan
2013-08-13 2:07 ` Li Zefan
2013-08-13 15:05 ` Tejun Heo
2013-08-13 15:05 ` Tejun Heo
[not found] ` <20130813150549.GF26596-9pTldWuhBndy/B6EtB590w@public.gmane.org>
2013-08-14 2:01 ` Li Zefan [this message]
2013-08-14 2:01 ` Li Zefan
[not found] ` <520AE4FC.5090702-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-08-14 13:30 ` Tejun Heo
2013-08-14 13:30 ` Tejun Heo
[not found] ` <20130814133048.GC28628-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-08-16 6:48 ` Li Zefan
2013-08-16 6:48 ` Li Zefan
2013-08-13 14:53 ` [PATCH 1/2] cpuset: remove an unncessary forward declaration Tejun Heo
2013-08-13 14:53 ` Tejun Heo
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