From: Daniel Wagner <wagi-kQCPcA+X3s7YtjvyW6yDsg@public•gmane.org>
To: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public•gmane.org>
Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
Daniel Wagner
<daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public•gmane.org>,
Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public•gmane.org>,
Jamal Hadi Salim <jhs-jkUAjuhPggJWk0Htik3J/w@public•gmane.org>,
John Fastabend
<john.r.fastabend-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org>,
Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public•gmane.org>
Subject: Re: [PATCH v4 4/8] cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT
Date: Thu, 13 Sep 2012 09:38:54 +0200 [thread overview]
Message-ID: <50518D8E.5020206@monom.org> (raw)
In-Reply-To: <505187C8.9030001-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Hi Li,
On 13.09.2012 09:14, Li Zefan wrote:
> On 2012/9/13 14:57, Daniel Wagner wrote:
>> Hi Li,
>>
>> On 13.09.2012 08:41, Li Zefan wrote:
>>>> @@ -1321,11 +1321,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
>>>> * take duplicate reference counts on a subsystem that's already used,
>>>> * but rebind_subsystems handles this case.
>>>> */
>>>> - for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
>>>> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
>>>> unsigned long bit = 1UL << i;
>>>>
>>>> if (!(bit & opts->subsys_mask))
>>>> continue;
>>>> + if (!subsys[i]->module)
>>>> + continue;
>>>
>>> This check is not necessary. If it's builtin, try_module_get() will just return 1, and
>>> we're fine.
>>
>> Yes, I didn't see the try_module_get. Although I think with leaving the test away it would change the behavior, e.g.
>>
>> if (!subsys[i]->module)
>> continue;
>> if (!try_module_get(subsys[i]->module)) {
>> module_pin_failed = true;
>> break;
>> }
>>
>> module_pin_failed would be set then and we would jump into the error code later.
>>
>
> no behavioral change. For a builtin subsys, we won't run into the if block and have module_pin_failed be set.
Ah, I understand.
>> This tests looks a bit ugly though I think leaving it away and relying on try_module_get() is not correct.
>>
>
> I don't think this is bad. The block layer code does the similar thing in elevator_get().
>
> And we call module_put() unconditionally in rebind_subsys().
Okay, then these tests really not needed. I'll have them removed now
and tested the result. All works fine.
>>>> @@ -1437,6 +1443,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
>>>> INIT_LIST_HEAD(&cgrp->event_list);
>>>> spin_lock_init(&cgrp->event_list_lock);
>>>> simple_xattrs_init(&cgrp->xattrs);
>>>> + memset(cgrp->subsys, 0, sizeof(cgrp->subsys));
>>>
>>> This seems an unrelated change, and is redundant. Am I missing something?
>>
>> The reason why it is necessary to NULL all the entries in the array, is that task_cls_classid() and task_netprioidx() check the return pointer from task_subsys_state(). If it is NULL those function know that the subsystem is not ready to be used. Should I move this change to the next patch then?
>>
>
> It's already guaranteed the passing @cgrp is zeored. that's why cgrp->flags is not explicitly initialized here.
Stupid me, I didn't see the kzalloc. You are absolutely right.
Thanks for your review.
cheers,
daniel
next prev parent reply other threads:[~2012-09-13 7:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 14:12 [PATCH v4 0/8] cgroup: Assign subsystem IDs during compile time Daniel Wagner
2012-09-12 14:12 ` [PATCH v4 2/8] cgroup: net_cls: Do not define task_cls_classid() when not selected Daniel Wagner
2012-09-13 6:35 ` Li Zefan
2012-09-12 14:12 ` [PATCH v4 3/8] cgroup: net_prio: Do not define task_netpioidx() " Daniel Wagner
[not found] ` <1347459128-32236-4-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:36 ` Li Zefan
2012-09-12 14:12 ` [PATCH v4 4/8] cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT Daniel Wagner
[not found] ` <1347459128-32236-5-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:41 ` Li Zefan
[not found] ` <50517FFF.4030106-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-09-13 6:57 ` Daniel Wagner
[not found] ` <505183E3.3030409-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 7:14 ` Li Zefan
[not found] ` <505187C8.9030001-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-09-13 7:38 ` Daniel Wagner [this message]
2012-09-12 14:12 ` [PATCH v4 6/8] cgroup: Do not depend on a given order when populating the subsys array Daniel Wagner
[not found] ` <1347459128-32236-7-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:42 ` Li Zefan
2012-09-12 14:12 ` [PATCH v4 7/8] cgroup: Assign subsystem IDs during compile time Daniel Wagner
[not found] ` <1347459128-32236-8-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:45 ` Li Zefan
2012-09-12 14:12 ` [PATCH v4 8/8] cgroup: Define CGROUP_SUBSYS_COUNT according the configuration Daniel Wagner
[not found] ` <1347459128-32236-9-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:46 ` Li Zefan
[not found] ` <1347459128-32236-1-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-12 14:12 ` [PATCH v4 1/8] cgroup: net_cls: Move sock_update_classid() declaration to cls_cgroup.h Daniel Wagner
[not found] ` <1347459128-32236-2-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:34 ` Li Zefan
2012-09-12 14:12 ` [PATCH v4 5/8] cgroup: Wrap subsystem selection macro Daniel Wagner
[not found] ` <1347459128-32236-6-git-send-email-wagi-kQCPcA+X3s7YtjvyW6yDsg@public.gmane.org>
2012-09-13 6:41 ` Li Zefan
2012-09-12 18:56 ` [PATCH v4 0/8] cgroup: Assign subsystem IDs during compile time Tejun Heo
2012-09-13 14:01 ` Neil Horman
2012-09-13 18:13 ` Tejun Heo
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