From: Tejun Heo Subject: [PATCH 5/9] cgroup: move cgroup->sibling unlinking to cgroup_put() Date: Fri, 9 May 2014 17:13:31 -0400 Message-ID: <1399670015-23463-6-git-send-email-tj@kernel.org> References: <1399670015-23463-1-git-send-email-tj@kernel.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=cff60gbw+V2tuCPLOCQicHXGrcjg4XL2tonScR03Fls=; b=mScnanZTOwrsnNgKWK/lXkJsjuidZdUrOKtfW7sqf3BOxKb5ZXgV3UU3ezZn3bxTRz orISn11rFQxkk0GfkroSSOVwSoaRTnxE3j7eaGjkzMipY9m/c+PNzea9e1YOXnpGZmtn zo2fSexHXe7GJtHV5AcstDkJUDgBBMa309eM9xr5OXUW2OO6HKs46oTbQZ6Y+AIoWxGm kt9xanUK7NlhzUvxpFiuuSN9fN6MEVoLNjuP3aYUC98uC4Z+JDSxPxl+gZgtBMXFvUQm rCllymRrO+tYbboE6cZyj2Gl1M4bIeoJYmBPpw5xTIRhWffbQ2CB1fm1e25tkHfm5+wY CvHA== In-Reply-To: <1399670015-23463-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Tejun Heo Move cgroup->sibling unlinking from cgroup_destroy_css_killed() to cgroup_put(). This is later but still before the RCU grace period, so it doesn't break css_next_child() although there now is a larger window in which a dead cgroup is visible during css iteration. As css iteration always could have included offline csses, this doesn't affect correctness; however, it does make css_next_child() fall back to reiterting mode more often. This also makes cgroup_put() directly take cgroup_mutex, which limits where it can be called from. These are not immediately problematic and will be dealt with later. This change enables simplification of cgroup destruction path. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 45149b7..87ea2ce 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1056,6 +1056,11 @@ static void cgroup_put(struct cgroup *cgrp) if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp))) return; + /* delete this cgroup from parent->children */ + mutex_lock(&cgroup_mutex); + list_del_rcu(&cgrp->sibling); + mutex_unlock(&cgroup_mutex); + cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id); cgrp->id = -1; @@ -4560,9 +4565,6 @@ static void cgroup_destroy_css_killed(struct cgroup *cgrp) { lockdep_assert_held(&cgroup_mutex); - /* delete this cgroup from parent->children */ - list_del_rcu(&cgrp->sibling); - cgroup_put(cgrp); } -- 1.9.0