From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <493600A4.6040802@cn.fujitsu.com> Date: Wed, 03 Dec 2008 11:44:36 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [PATCH 1/3] cgroup: fix pre_destroy and semantics of css->refcnt References: <20081201145907.e6d63d61.kamezawa.hiroyu@jp.fujitsu.com> <20081201150208.6b24506b.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081201150208.6b24506b.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "menage@google.com" , "balbir@linux.vnet.ibm.com" , "nishimura@mxp.nes.nec.co.jp" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" List-ID: > +/* > + * Try to set all subsys's refcnt to be 0. > + * css->refcnt==0 means this subsys will be destroy()'d. > + */ > +static bool cgroup_set_subsys_removed(struct cgroup *cgrp) > +{ > + struct cgroup_subsys *ss; > + struct cgroup_subsys_state *css, *tmp; > + > + for_each_subsys(cgrp->root, ss) { > + css = cgrp->subsys[ss->subsys_id]; > + if (!atomic_dec_and_test(&css->refcnt)) > + goto rollback; > + } > + return true; > +rollback: > + for_each_subsys(cgrp->root, ss) { > + tmp = cgrp->subsys[ss->subsys_id]; > + atomic_inc(&tmp->refcnt); > + if (tmp == css) > + break; > + } > + return false; > +} > + This function may return false, then causes rmdir() fail. So css_tryget(subsys1) returns 0 doesn't necessarily mean subsys1->destroy() will be called, if subsys2's css's refcnt is >1 when cgroup_set_subsys_removed() is called. Will this bring up bugs and problems? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org