From ff0ce721ec213499ec5a532041fb3a1db2dc5ecb Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Sun, 4 Aug 2024 21:30:17 -0400 Subject: [PATCH] cgroup/cpuset: Eliminate unncessary sched domains rebuilds in hotplug It was found that some hotplug operations may cause multiple rebuild_sched_domains_locked() calls. Some of those intermediate calls may use cpuset states not in the final correct form leading to incorrect sched domain setting. Fix this problem by using the existing force_rebuild flag to inhibit immediate rebuild_sched_domains_locked() calls if set and only doing one final call at the end. Also renaming the force_rebuild flag to force_sd_rebuild to make its meaning for clear. Signed-off-by: Waiman Long Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 97d02612b3a6..4bd9e50bcc8e 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -232,6 +232,13 @@ static cpumask_var_t isolated_cpus; /* List of remote partition root children */ static struct list_head remote_children; +/* + * A flag to force sched domain rebuild at the end of an operation while + * inhibiting it in the intermediate stages when set. Currently it is only + * set in hotplug code. + */ +static bool force_sd_rebuild; + /* * Partition root states: * @@ -1475,7 +1482,7 @@ static void update_partition_sd_lb(struct cpuset *cs, int old_prs) clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags); } - if (rebuild_domains) + if (rebuild_domains && !force_sd_rebuild) rebuild_sched_domains_locked(); } @@ -1833,7 +1840,7 @@ static void remote_partition_check(struct cpuset *cs, struct cpumask *newmask, remote_partition_disable(child, tmp); disable_cnt++; } - if (disable_cnt) + if (disable_cnt && !force_sd_rebuild) rebuild_sched_domains_locked(); } @@ -2442,7 +2449,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, } rcu_read_unlock(); - if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD)) + if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD) && + !force_sd_rebuild) rebuild_sched_domains_locked(); } @@ -3104,7 +3112,8 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, cs->flags = trialcs->flags; spin_unlock_irq(&callback_lock); - if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed) + if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed && + !force_sd_rebuild) rebuild_sched_domains_locked(); if (spread_flag_changed) @@ -4501,11 +4510,9 @@ hotplug_update_tasks(struct cpuset *cs, update_tasks_nodemask(cs); } -static bool force_rebuild; - void cpuset_force_rebuild(void) { - force_rebuild = true; + force_sd_rebuild = true; } /** @@ -4653,15 +4660,9 @@ static void cpuset_handle_hotplug(void) !cpumask_empty(subpartitions_cpus); mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems); - /* - * In the rare case that hotplug removes all the cpus in - * subpartitions_cpus, we assumed that cpus are updated. - */ - if (!cpus_updated && !cpumask_empty(subpartitions_cpus)) - cpus_updated = true; - /* For v1, synchronize cpus_allowed to cpu_active_mask */ if (cpus_updated) { + cpuset_force_rebuild(); spin_lock_irq(&callback_lock); if (!on_dfl) cpumask_copy(top_cpuset.cpus_allowed, &new_cpus); @@ -4717,8 +4718,8 @@ static void cpuset_handle_hotplug(void) } /* rebuild sched domains if cpus_allowed has changed */ - if (cpus_updated || force_rebuild) { - force_rebuild = false; + if (force_sd_rebuild) { + force_sd_rebuild = false; rebuild_sched_domains_cpuslocked(); }