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cgroup/cpuset: Eliminate unncessary sched domains rebuilds in hotplug

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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 <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2024-08-04 21:30:17 -04:00 • committed by Tejun Heo
parent 311a1bdc44
commit ff0ce721ec
1 changed files with 17 additions and 16 deletions
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33
kernel/cgroup/cpuset.c
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@ -232,6 +232,13 @@ static cpumask_var_t isolated_cpus;
/* List of remote partition root children */ /* List of remote partition root children */
static struct list_head remote_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: * 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); clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
} }
if (rebuild_domains) if (rebuild_domains && !force_sd_rebuild)
rebuild_sched_domains_locked(); rebuild_sched_domains_locked();
} }
@ -1833,7 +1840,7 @@ static void remote_partition_check(struct cpuset *cs, struct cpumask *newmask,
remote_partition_disable(child, tmp); remote_partition_disable(child, tmp);
disable_cnt++; disable_cnt++;
} }
if (disable_cnt) if (disable_cnt && !force_sd_rebuild)
rebuild_sched_domains_locked(); rebuild_sched_domains_locked();
} }
@ -2442,7 +2449,8 @@ get_css:
} }
rcu_read_unlock(); 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(); rebuild_sched_domains_locked();
} }
@ -3104,7 +3112,8 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
cs->flags = trialcs->flags; cs->flags = trialcs->flags;
spin_unlock_irq(&callback_lock); 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(); rebuild_sched_domains_locked();
if (spread_flag_changed) if (spread_flag_changed)
@ -4501,11 +4510,9 @@ hotplug_update_tasks(struct cpuset *cs,
update_tasks_nodemask(cs); update_tasks_nodemask(cs);
} }
static bool force_rebuild;
void cpuset_force_rebuild(void) 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); !cpumask_empty(subpartitions_cpus);
mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems); 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 */ /* For v1, synchronize cpus_allowed to cpu_active_mask */
if (cpus_updated) { if (cpus_updated) {
cpuset_force_rebuild();
spin_lock_irq(&callback_lock); spin_lock_irq(&callback_lock);
if (!on_dfl) if (!on_dfl)
cpumask_copy(top_cpuset.cpus_allowed, &new_cpus); 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 */ /* rebuild sched domains if cpus_allowed has changed */
if (cpus_updated || force_rebuild) { if (force_sd_rebuild) {
force_rebuild = false; force_sd_rebuild = false;
rebuild_sched_domains_cpuslocked(); rebuild_sched_domains_cpuslocked();
} }