Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932427Ab2JZLj2 (ORCPT ); Fri, 26 Oct 2012 07:39:28 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57431 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932351Ab2JZLiF (ORCPT ); Fri, 26 Oct 2012 07:38:05 -0400 From: Michal Hocko To: linux-mm@kvack.org Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Tejun Heo , Li Zefan , Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh , Glauber Costa Subject: [PATCH v3 4/6] cgroups: forbid pre_destroy callback to fail Date: Fri, 26 Oct 2012 13:37:31 +0200 Message-Id: <1351251453-6140-5-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1351251453-6140-1-git-send-email-mhocko@suse.cz> References: <1351251453-6140-1-git-send-email-mhocko@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3126 Lines: 105 Now that mem_cgroup_pre_destroy callback doesn't fail (other than a race with a task attach resp. child group appears) finally we can safely move on and forbit all the callbacks to fail. The last missing piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so that css_tryget fails so no new charges for the memcg can happen. We cannot, however, move cgroup_call_pre_destroy right after because we cannot call mem_cgroup_pre_destroy with the cgroup_lock held (see 3fa59dfb cgroup: fix potential deadlock in pre_destroy) so we have to move it after the lock is released. Changes since v1 - Li Zefan pointed out that mem_cgroup_pre_destroy cannot be called with cgroup_lock held Signed-off-by: Michal Hocko --- kernel/cgroup.c | 30 +++++++++--------------------- 1 file changed, 9 insertions(+), 21 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7981850..e9e2287b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -855,7 +855,7 @@ static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb) * Call subsys's pre_destroy handler. * This is called before css refcnt check. */ -static int cgroup_call_pre_destroy(struct cgroup *cgrp) +static void cgroup_call_pre_destroy(struct cgroup *cgrp) { struct cgroup_subsys *ss; int ret = 0; @@ -864,15 +864,8 @@ static int cgroup_call_pre_destroy(struct cgroup *cgrp) if (!ss->pre_destroy) continue; - ret = ss->pre_destroy(cgrp); - if (ret) { - /* ->pre_destroy() failure is being deprecated */ - WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs); - break; - } + BUG_ON(ss->pre_destroy(cgrp)); } - - return ret; } static void cgroup_diput(struct dentry *dentry, struct inode *inode) @@ -4151,7 +4144,6 @@ again: mutex_unlock(&cgroup_mutex); return -EBUSY; } - mutex_unlock(&cgroup_mutex); /* * In general, subsystem has no css->refcnt after pre_destroy(). But @@ -4164,17 +4156,6 @@ again: */ set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); - /* - * Call pre_destroy handlers of subsys. Notify subsystems - * that rmdir() request comes. - */ - ret = cgroup_call_pre_destroy(cgrp); - if (ret) { - clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); - return ret; - } - - mutex_lock(&cgroup_mutex); parent = cgrp->parent; if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) { clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); @@ -4196,6 +4177,7 @@ again: return -EINTR; goto again; } + /* NO css_tryget() can success after here. */ finish_wait(&cgroup_rmdir_waitq, &wait); clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); @@ -4234,6 +4216,12 @@ again: spin_unlock(&cgrp->event_list_lock); mutex_unlock(&cgroup_mutex); + + /* + * Call pre_destroy handlers of subsys. Notify subsystems + * that rmdir() request comes. + */ + cgroup_call_pre_destroy(cgrp); return 0; } -- 1.7.10.4 -- 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/