From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Wagner Subject: Re: [PATCH v4 4/8] cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT Date: Thu, 13 Sep 2012 09:38:54 +0200 Message-ID: <50518D8E.5020206@monom.org> References: <1347459128-32236-1-git-send-email-wagi@monom.org> <1347459128-32236-5-git-send-email-wagi@monom.org> <50517FFF.4030106@huawei.com> <505183E3.3030409@monom.org> <505187C8.9030001@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <505187C8.9030001-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Li Zefan Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Daniel Wagner , Gao feng , Jamal Hadi Salim , John Fastabend , Neil Horman 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