From: Sebastian Andrzej Siewior Date: Thu, 15 Aug 2019 18:14:16 +0200 Subject: [PATCH 1/4] cgroup: Remove ->css_rstat_flush() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.17-rt8.tar.xz I was looking at the lifetime of the the ->css_rstat_flush() to see if cgroup_rstat_cpu_lock should remain a raw_spinlock_t. I didn't find any users and is unused since it was introduced in commit 8f53470bab042 ("cgroup: Add cgroup_subsys->css_rstat_flush()") Remove the css_rstat_flush callback because it has no users. Signed-off-by: Sebastian Andrzej Siewior --- include/linux/cgroup-defs.h | 5 ----- kernel/cgroup/cgroup.c | 12 ------------ kernel/cgroup/rstat.c | 10 +--------- 3 files changed, 1 insertion(+), 26 deletions(-) --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -144,9 +144,6 @@ struct cgroup_subsys_state { struct list_head sibling; struct list_head children; - /* flush target list anchored at cgrp->rstat_css_list */ - struct list_head rstat_css_node; - /* * PI: Subsys-unique ID. 0 is unused and root is always 1. The * matching css can be looked up using css_from_id(). @@ -455,7 +452,6 @@ struct cgroup { /* per-cpu recursive resource statistics */ struct cgroup_rstat_cpu __percpu *rstat_cpu; - struct list_head rstat_css_list; /* cgroup basic resource statistics */ struct cgroup_base_stat pending_bstat; /* pending from children */ @@ -633,7 +629,6 @@ struct cgroup_subsys { void (*css_released)(struct cgroup_subsys_state *css); void (*css_free)(struct cgroup_subsys_state *css); void (*css_reset)(struct cgroup_subsys_state *css); - void (*css_rstat_flush)(struct cgroup_subsys_state *css, int cpu); int (*css_extra_stat_show)(struct seq_file *seq, struct cgroup_subsys_state *css); --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1957,7 +1957,6 @@ static void init_cgroup_housekeeping(str cgrp->dom_cgrp = cgrp; cgrp->max_descendants = INT_MAX; cgrp->max_depth = INT_MAX; - INIT_LIST_HEAD(&cgrp->rstat_css_list); prev_cputime_init(&cgrp->prev_cputime); for_each_subsys(ss, ssid) @@ -5013,12 +5012,6 @@ static void css_release_work_fn(struct w list_del_rcu(&css->sibling); if (ss) { - /* css release path */ - if (!list_empty(&css->rstat_css_node)) { - cgroup_rstat_flush(cgrp); - list_del_rcu(&css->rstat_css_node); - } - cgroup_idr_replace(&ss->css_idr, NULL, css->id); if (ss->css_released) ss->css_released(css); @@ -5080,7 +5073,6 @@ static void init_and_link_css(struct cgr css->id = -1; INIT_LIST_HEAD(&css->sibling); INIT_LIST_HEAD(&css->children); - INIT_LIST_HEAD(&css->rstat_css_node); css->serial_nr = css_serial_nr_next++; atomic_set(&css->online_cnt, 0); @@ -5089,9 +5081,6 @@ static void init_and_link_css(struct cgr css_get(css->parent); } - if (cgroup_on_dfl(cgrp) && ss->css_rstat_flush) - list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list); - BUG_ON(cgroup_css(cgrp, ss)); } @@ -5193,7 +5182,6 @@ static struct cgroup_subsys_state *css_c err_list_del: list_del_rcu(&css->sibling); err_free_css: - list_del_rcu(&css->rstat_css_node); INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); return ERR_PTR(err); --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -162,17 +162,9 @@ static void cgroup_rstat_flush_locked(st struct cgroup *pos = NULL; raw_spin_lock(cpu_lock); - while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) { - struct cgroup_subsys_state *css; - + while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) cgroup_base_stat_flush(pos, cpu); - rcu_read_lock(); - list_for_each_entry_rcu(css, &pos->rstat_css_list, - rstat_css_node) - css->ss->css_rstat_flush(css, cpu); - rcu_read_unlock(); - } raw_spin_unlock(cpu_lock); /* if @may_sleep, play nice and yield if necessary */