Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754791AbbDXN7f (ORCPT ); Fri, 24 Apr 2015 09:59:35 -0400 Received: from mail-ig0-f180.google.com ([209.85.213.180]:36211 "EHLO mail-ig0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752511AbbDXN7b (ORCPT ); Fri, 24 Apr 2015 09:59:31 -0400 MIME-Version: 1.0 X-Originating-IP: [122.106.150.15] In-Reply-To: <20150422155445.GD10738@htj.duckdns.org> References: <1429446154-10660-1-git-send-email-cyphar@cyphar.com> <1429446154-10660-4-git-send-email-cyphar@cyphar.com> <20150422155445.GD10738@htj.duckdns.org> Date: Fri, 24 Apr 2015 23:59:31 +1000 Message-ID: Subject: Re: [PATCH v10 3/4] cgroups: allow a cgroup subsystem to reject a fork From: Aleksa Sarai To: Tejun Heo Cc: lizefan@huawei.com, mingo@redhat.com, peterz@infradead.org, richard@nod.at, =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2080 Lines: 58 Hey, >> +#define CGROUP_PREFORK_COUNT 0 >> + >> static inline int cgroup_init_early(void) { return 0; } >> static inline int cgroup_init(void) { return 0; } >> static inline void cgroup_fork(struct task_struct *p) {} >> -static inline void cgroup_post_fork(struct task_struct *p) {} >> +static inline int cgroup_can_fork(struct task_struct *p, >> + void *s[CGROUP_PREFORK_COUNT]) >> +{ >> + return 0; >> +} > > Style consistency? It's because it wraps. I can move it to be something like: static inline int cgroup_can_fork(struct task_struct *p, void *s[CGROUP_PREFORK_COUNT]) { return 0; } If you like. >> @@ -2078,6 +2084,18 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, >> list_move_tail(&tsk->cg_list, &new_cset->mg_tasks); >> >> /* >> + * We detach from the old_cset subsystems here. We must do this >> + * before we drop the refcount for old_cset, in order to make sure >> + * that nobody frees it underneath us. >> + */ >> + for_each_e_css(css, i, old_cgrp) { >> + struct cgroup_subsys_state *old_css = old_cset->subsys[i]; >> + >> + if (old_css->ss->detach) >> + old_css->ss->detach(old_css, tsk); >> + } > > I don't get this. What can ->detach do that ->can_attach cannot? ->detach signifies that a task is being migrated away from a cgroup. On second thought, we could just use task_css() on each task in the tset to figure out what the cgroup the task is being migrated away from is and just uncharge that inside ->can_attach. On the same point, are all the tasks in a tset passed to ->can_attach guaranteed to have the same css? Or do I have to uncharge each one individually? -- Aleksa Sarai (cyphar) www.cyphar.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/