From 6f3d828f0fb7fdaffc6f32cb8a1cb7fcf8824598 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 12 Jun 2013 21:04:55 -0700 Subject: [PATCH] cgroup: remove cgroup->count and use cgroup->count tracks the number of css_sets associated with the cgroup and used only to verify that no css_set is associated when the cgroup is being destroyed. It's superflous as the destruction path can simply check whether cgroup->cset_links is empty instead. Drop cgroup->count and check ->cset_links directly from cgroup_destroy_locked(). Signed-off-by: Tejun Heo Acked-by: Li Zefan --- include/linux/cgroup.h | 6 ------ kernel/cgroup.c | 21 +++++---------------- 2 files changed, 5 insertions(+), 22 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c86a93abe83d..81bfd0268e93 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -169,12 +169,6 @@ struct cgroup_name { struct cgroup { unsigned long flags; /* "unsigned long" so bitops work */ - /* - * count users of this cgroup. >0 means busy, but doesn't - * necessarily indicate the number of tasks in the cgroup - */ - atomic_t count; - int id; /* ida allocated in-hierarchy ID */ /* diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1a68241ca835..49bfd7b0bbda 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -408,8 +408,7 @@ static void __put_css_set(struct css_set *cset, int taskexit) list_del(&link->cgrp_link); /* @cgrp can't go away while we're holding css_set_lock */ - if (atomic_dec_and_test(&cgrp->count) && - notify_on_release(cgrp)) { + if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) { if (taskexit) set_bit(CGRP_RELEASABLE, &cgrp->flags); check_for_release(cgrp); @@ -616,7 +615,6 @@ static void link_css_set(struct list_head *tmp_links, struct css_set *cset, link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link); link->cset = cset; link->cgrp = cgrp; - atomic_inc(&cgrp->count); list_move(&link->cset_link, &cgrp->cset_links); /* * Always add links to the tail of the list so that the list @@ -4370,11 +4368,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) lockdep_assert_held(&cgroup_mutex); /* - * css_set_lock prevents @cgrp from being removed while - * __put_css_set() is in progress. + * css_set_lock synchronizes access to ->cset_links and prevents + * @cgrp from being removed while __put_css_set() is in progress. */ read_lock(&css_set_lock); - empty = !atomic_read(&cgrp->count) && list_empty(&cgrp->children); + empty = list_empty(&cgrp->cset_links) && list_empty(&cgrp->children); read_unlock(&css_set_lock); if (!empty) return -EBUSY; @@ -5054,7 +5052,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) static void check_for_release(struct cgroup *cgrp) { if (cgroup_is_releasable(cgrp) && - !atomic_read(&cgrp->count) && list_empty(&cgrp->children)) { + list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) { /* * Control Group is currently removeable. If it's not * already queued for a userspace notification, queue @@ -5422,11 +5420,6 @@ static void debug_css_free(struct cgroup *cont) kfree(cont->subsys[debug_subsys_id]); } -static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft) -{ - return atomic_read(&cont->count); -} - static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft) { return cgroup_task_count(cont); @@ -5507,10 +5500,6 @@ static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft) } static struct cftype debug_files[] = { - { - .name = "cgroup_refcount", - .read_u64 = cgroup_refcount_read, - }, { .name = "taskcount", .read_u64 = debug_taskcount_read, -- 2.39.5