cpuset: drop async_rebuild_sched_domains()
In general, we want to make cgroup_mutex one of the outermost locks and be able to use get_online_cpus() and friends from cgroup methods. With cpuset hotplug made async, get_online_cpus() can now be nested inside cgroup_mutex. Currently, cpuset avoids nesting get_online_cpus() inside cgroup_mutex by bouncing sched_domain rebuilding to a work item. As such nesting is allowed now, remove the workqueue bouncing code and always rebuild sched_domains synchronously. This also nests sched_domains_mutex inside cgroup_mutex, which is intended and should be okay. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
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@ -60,14 +60,6 @@
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#include <linux/workqueue.h>
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#include <linux/workqueue.h>
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#include <linux/cgroup.h>
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#include <linux/cgroup.h>
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/*
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* Workqueue for cpuset related tasks.
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*
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* Using kevent workqueue may cause deadlock when memory_migrate
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* is set. So we create a separate workqueue thread for cpuset.
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*/
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static struct workqueue_struct *cpuset_wq;
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/*
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/*
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* Tracks how many cpusets are currently defined in system.
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* Tracks how many cpusets are currently defined in system.
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* When there is only one cpuset (the root cpuset) we can
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* When there is only one cpuset (the root cpuset) we can
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@ -753,25 +745,25 @@ done:
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/*
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/*
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* Rebuild scheduler domains.
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* Rebuild scheduler domains.
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*
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*
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* Call with neither cgroup_mutex held nor within get_online_cpus().
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* If the flag 'sched_load_balance' of any cpuset with non-empty
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* Takes both cgroup_mutex and get_online_cpus().
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* 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
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* which has that flag enabled, or if any cpuset with a non-empty
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* 'cpus' is removed, then call this routine to rebuild the
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* scheduler's dynamic sched domains.
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*
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*
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* Cannot be directly called from cpuset code handling changes
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* Call with cgroup_mutex held. Takes get_online_cpus().
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* to the cpuset pseudo-filesystem, because it cannot be called
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* from code that already holds cgroup_mutex.
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*/
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*/
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static void do_rebuild_sched_domains(struct work_struct *unused)
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static void rebuild_sched_domains_locked(void)
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{
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{
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struct sched_domain_attr *attr;
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struct sched_domain_attr *attr;
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cpumask_var_t *doms;
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cpumask_var_t *doms;
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int ndoms;
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int ndoms;
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WARN_ON_ONCE(!cgroup_lock_is_held());
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get_online_cpus();
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get_online_cpus();
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/* Generate domain masks and attrs */
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/* Generate domain masks and attrs */
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cgroup_lock();
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ndoms = generate_sched_domains(&doms, &attr);
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ndoms = generate_sched_domains(&doms, &attr);
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cgroup_unlock();
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/* Have scheduler rebuild the domains */
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/* Have scheduler rebuild the domains */
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partition_sched_domains(ndoms, doms, attr);
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partition_sched_domains(ndoms, doms, attr);
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@ -779,7 +771,7 @@ static void do_rebuild_sched_domains(struct work_struct *unused)
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put_online_cpus();
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put_online_cpus();
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}
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}
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#else /* !CONFIG_SMP */
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#else /* !CONFIG_SMP */
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static void do_rebuild_sched_domains(struct work_struct *unused)
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static void rebuild_sched_domains_locked(void)
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{
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{
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}
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}
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@ -791,44 +783,11 @@ static int generate_sched_domains(cpumask_var_t **domains,
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}
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}
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#endif /* CONFIG_SMP */
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#endif /* CONFIG_SMP */
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static DECLARE_WORK(rebuild_sched_domains_work, do_rebuild_sched_domains);
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/*
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* Rebuild scheduler domains, asynchronously via workqueue.
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*
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* If the flag 'sched_load_balance' of any cpuset with non-empty
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* 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
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* which has that flag enabled, or if any cpuset with a non-empty
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* 'cpus' is removed, then call this routine to rebuild the
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* scheduler's dynamic sched domains.
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*
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* The rebuild_sched_domains() and partition_sched_domains()
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* routines must nest cgroup_lock() inside get_online_cpus(),
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* but such cpuset changes as these must nest that locking the
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* other way, holding cgroup_lock() for much of the code.
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*
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* So in order to avoid an ABBA deadlock, the cpuset code handling
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* these user changes delegates the actual sched domain rebuilding
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* to a separate workqueue thread, which ends up processing the
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* above do_rebuild_sched_domains() function.
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*/
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static void async_rebuild_sched_domains(void)
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{
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queue_work(cpuset_wq, &rebuild_sched_domains_work);
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}
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/*
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* Accomplishes the same scheduler domain rebuild as the above
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* async_rebuild_sched_domains(), however it directly calls the
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* rebuild routine synchronously rather than calling it via an
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* asynchronous work thread.
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*
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* This can only be called from code that is not holding
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* cgroup_mutex (not nested in a cgroup_lock() call.)
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*/
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void rebuild_sched_domains(void)
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void rebuild_sched_domains(void)
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{
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{
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do_rebuild_sched_domains(NULL);
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cgroup_lock();
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rebuild_sched_domains_locked();
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cgroup_unlock();
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}
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}
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/**
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/**
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@ -948,7 +907,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
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heap_free(&heap);
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heap_free(&heap);
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if (is_load_balanced)
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if (is_load_balanced)
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async_rebuild_sched_domains();
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rebuild_sched_domains_locked();
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return 0;
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return 0;
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}
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}
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@ -1196,7 +1155,7 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
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cs->relax_domain_level = val;
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cs->relax_domain_level = val;
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if (!cpumask_empty(cs->cpus_allowed) &&
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if (!cpumask_empty(cs->cpus_allowed) &&
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is_sched_load_balance(cs))
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is_sched_load_balance(cs))
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async_rebuild_sched_domains();
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rebuild_sched_domains_locked();
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}
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}
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return 0;
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return 0;
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@ -1288,7 +1247,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
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mutex_unlock(&callback_mutex);
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mutex_unlock(&callback_mutex);
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if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
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if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
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async_rebuild_sched_domains();
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rebuild_sched_domains_locked();
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if (spread_flag_changed)
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if (spread_flag_changed)
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update_tasks_flags(cs, &heap);
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update_tasks_flags(cs, &heap);
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@ -1925,7 +1884,7 @@ static void cpuset_css_offline(struct cgroup *cgrp)
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/*
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/*
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* If the cpuset being removed has its flag 'sched_load_balance'
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* If the cpuset being removed has its flag 'sched_load_balance'
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* enabled, then simulate turning sched_load_balance off, which
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* enabled, then simulate turning sched_load_balance off, which
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* will call async_rebuild_sched_domains().
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* will call rebuild_sched_domains_locked().
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*/
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*/
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static void cpuset_css_free(struct cgroup *cont)
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static void cpuset_css_free(struct cgroup *cont)
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@ -2237,9 +2196,6 @@ void __init cpuset_init_smp(void)
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top_cpuset.mems_allowed = node_states[N_MEMORY];
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top_cpuset.mems_allowed = node_states[N_MEMORY];
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hotplug_memory_notifier(cpuset_track_online_nodes, 10);
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hotplug_memory_notifier(cpuset_track_online_nodes, 10);
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cpuset_wq = create_singlethread_workqueue("cpuset");
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BUG_ON(!cpuset_wq);
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}
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}
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/**
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/**
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