From: Daniel Wagner <wagi@monom•org>
To: Tejun Heo <tj@kernel•org>
Cc: netdev@vger•kernel.org, cgroups@vger•kernel.org,
"David S. Miller" <davem@davemloft•net>,
Gao feng <gaofeng@cn•fujitsu.com>,
Jamal Hadi Salim <jhs@mojatatu•com>,
John Fastabend <john.r.fastabend@intel•com>,
Li Zefan <lizefan@huawei•com>,
Neil Horman <nhorman@tuxdriver•com>
Subject: Re: [PATCH v2 03/10] cgroup: net_cls: Protect access to task_cls_classid() when built as module
Date: Sat, 25 Aug 2012 18:56:29 +0200 [thread overview]
Message-ID: <503903BD.6020208@monom.org> (raw)
In-Reply-To: <20120824232621.GQ21325@google.com>
On 25.08.2012 01:26, Tejun Heo wrote:
> On Fri, Aug 24, 2012 at 04:01:37PM +0200, Daniel Wagner wrote:
>> @@ -306,6 +312,11 @@ static void __exit exit_cgroup_cls(void)
>> synchronize_rcu();
>> #endif
>>
>> +#if IS_MODULE(CONFIG_NET_CLS_CGROUP)
>> + static_key_slow_dec(&cgroup_cls_enabled);
>> + rcu_barrier();
>
> Why is this rcu_barrier() necessary?
I have read the rcubarrier.txt document and I got from that that an
rcu_barrier() is needed when unloading a module. But maybe I got it wrong.
So the idea after disabling the jump lables all pending readers in
task_cls_classid() have left. THe same thing is done in the old code
with the dynamic id part. With the difference that synchronize_rcu() is
used.
> In general, please explain what
> synchronization is going on when using sync constructs which aren't
> obvious - e.g. memory barriers, rcu barriers.
Sure, I will keep this in mind.
next prev parent reply other threads:[~2012-08-25 16:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-24 14:01 [PATCH v2 00/10] cgroup: Assign subsystem IDs during compile time Daniel Wagner
2012-08-24 14:01 ` [PATCH v2 01/10] cgroup: net_cls: Use empty task_cls_classid() when !CONFIG_NET_CLS(_MODULE) Daniel Wagner
[not found] ` <1345816904-21745-2-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:22 ` Tejun Heo
2012-08-27 2:32 ` Li Zefan
2012-08-24 14:01 ` [PATCH v2 03/10] cgroup: net_cls: Protect access to task_cls_classid() when built as module Daniel Wagner
[not found] ` <1345816904-21745-4-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:26 ` Tejun Heo
2012-08-25 16:56 ` Daniel Wagner [this message]
[not found] ` <503903BD.6020208-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-28 14:47 ` Paul E. McKenney
[not found] ` <20120828144725.GR2961-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2012-08-28 16:41 ` Daniel Wagner
2012-08-24 14:01 ` [PATCH v2 05/10] cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT Daniel Wagner
[not found] ` <1345816904-21745-6-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:28 ` Tejun Heo
[not found] ` <20120824232840.GS21325-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-08-25 16:59 ` Daniel Wagner
[not found] ` <5039046D.1040402-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-06 22:23 ` Tejun Heo
2012-08-24 14:01 ` [PATCH v2 06/10] cgroup: Assign subsystem IDs during compile time Daniel Wagner
[not found] ` <1345816904-21745-7-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:38 ` Tejun Heo
[not found] ` <20120824233810.GT21325-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-08-25 17:11 ` Daniel Wagner
[not found] ` <50390743.2090203-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-06 22:32 ` Tejun Heo
2012-08-24 14:01 ` [PATCH v2 08/10] cgroup: net_cls: Merge builtin and module version of task_cls_classid() Daniel Wagner
[not found] ` <1345816904-21745-9-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:41 ` Tejun Heo
[not found] ` <1345816904-21745-1-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 14:01 ` [PATCH v2 02/10] cgroup: net_cls: Move sock_update_classid() decleration to cls_cgroup.h Daniel Wagner
2012-08-24 14:01 ` [PATCH v2 04/10] cgroup: net_prio: Protect access to task_netprioidx() when built as module Daniel Wagner
[not found] ` <1345816904-21745-5-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:26 ` Tejun Heo
2012-08-24 14:01 ` [PATCH v2 07/10] cgroup: net_cls: Simplify ifdef logic Daniel Wagner
[not found] ` <1345816904-21745-8-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:39 ` Tejun Heo
2012-08-24 14:01 ` [PATCH v2 09/10] cgroup: net_prio: " Daniel Wagner
[not found] ` <1345816904-21745-10-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-08-24 23:42 ` Tejun Heo
2012-08-24 14:01 ` [PATCH v2 10/10] cgroup: net_prio: Merge builtin and module version of task_netprioidx() Daniel Wagner
2012-08-24 15:01 ` [PATCH v2 00/10] cgroup: Assign subsystem IDs during compile time Daniel Wagner
2012-08-24 23:15 ` Tejun Heo
[not found] ` <20120824231528.GO21325-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-08-25 16:49 ` Daniel Wagner
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