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Revert "cgroup/cpuset: remove circular dependency deadlock"

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This reverts commit aa24163b2e.

This and the following commit led to another circular locking scenario
and the scenario which is fixed by this commit no longer exists after
e8b3f8db7a ("workqueue/hotplug: simplify workqueue_offline_cpu()")
which removes work item flushing from hotplug path.

Revert it for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2017-12-04 14:55:59 -08:00
parent 11db855c3d
commit bdfbbda90a
1 changed files with 23 additions and 30 deletions
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53
kernel/cgroup/cpuset.c
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@ -812,18 +812,6 @@ done:
return ndoms;
}
static void cpuset_sched_change_begin(void)
{
cpus_read_lock();
mutex_lock(&cpuset_mutex);
}
static void cpuset_sched_change_end(void)
{
mutex_unlock(&cpuset_mutex);
cpus_read_unlock();
}
/*
* Rebuild scheduler domains.
*
@ -833,14 +821,16 @@ static void cpuset_sched_change_end(void)
* 'cpus' is removed, then call this routine to rebuild the
* scheduler's dynamic sched domains.
*
* Call with cpuset_mutex held. Takes get_online_cpus().
*/
static void rebuild_sched_domains_cpuslocked(void)
static void rebuild_sched_domains_locked(void)
{
struct sched_domain_attr *attr;
cpumask_var_t *doms;
int ndoms;
lockdep_assert_held(&cpuset_mutex);
get_online_cpus();
/*
* We have raced with CPU hotplug. Don't do anything to avoid
@ -848,25 +838,27 @@ static void rebuild_sched_domains_cpuslocked(void)
* Anyways, hotplug work item will rebuild sched domains.
*/
if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
return;
goto out;
/* Generate domain masks and attrs */
ndoms = generate_sched_domains(&doms, &attr);
/* Have scheduler rebuild the domains */
partition_sched_domains(ndoms, doms, attr);
out:
put_online_cpus();
}
#else /* !CONFIG_SMP */
static void rebuild_sched_domains_cpuslocked(void)
static void rebuild_sched_domains_locked(void)
{
}
#endif /* CONFIG_SMP */
void rebuild_sched_domains(void)
{
cpuset_sched_change_begin();
rebuild_sched_domains_cpuslocked();
cpuset_sched_change_end();
mutex_lock(&cpuset_mutex);
rebuild_sched_domains_locked();
mutex_unlock(&cpuset_mutex);
}
/**
@ -952,7 +944,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
rcu_read_unlock();
if (need_rebuild_sched_domains)
rebuild_sched_domains_cpuslocked();
rebuild_sched_domains_locked();
}
/**
@ -1284,7 +1276,7 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
cs->relax_domain_level = val;
if (!cpumask_empty(cs->cpus_allowed) &&
is_sched_load_balance(cs))
rebuild_sched_domains_cpuslocked();
rebuild_sched_domains_locked();
}
return 0;
@ -1317,6 +1309,7 @@ static void update_tasks_flags(struct cpuset *cs)
*
* Call with cpuset_mutex held.
*/
static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
int turning_on)
{
@ -1349,7 +1342,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
spin_unlock_irq(&callback_lock);
if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
rebuild_sched_domains_cpuslocked();
rebuild_sched_domains_locked();
if (spread_flag_changed)
update_tasks_flags(cs);
@ -1617,7 +1610,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
cpuset_filetype_t type = cft->private;
int retval = 0;
cpuset_sched_change_begin();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) {
retval = -ENODEV;
goto out_unlock;
@ -1653,7 +1646,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
break;
}
out_unlock:
cpuset_sched_change_end();
mutex_unlock(&cpuset_mutex);
return retval;
}
@ -1664,7 +1657,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
cpuset_filetype_t type = cft->private;
int retval = -ENODEV;
cpuset_sched_change_begin();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -1677,7 +1670,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
break;
}
out_unlock:
cpuset_sched_change_end();
mutex_unlock(&cpuset_mutex);
return retval;
}
@ -1716,7 +1709,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
kernfs_break_active_protection(of->kn);
flush_work(&cpuset_hotplug_work);
cpuset_sched_change_begin();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -1740,7 +1733,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
free_trial_cpuset(trialcs);
out_unlock:
cpuset_sched_change_end();
mutex_unlock(&cpuset_mutex);
kernfs_unbreak_active_protection(of->kn);
css_put(&cs->css);
flush_workqueue(cpuset_migrate_mm_wq);
@ -2041,14 +2034,14 @@ out_unlock:
/*
* If the cpuset being removed has its flag 'sched_load_balance'
* enabled, then simulate turning sched_load_balance off, which
* will call rebuild_sched_domains_cpuslocked().
* will call rebuild_sched_domains_locked().
*/
static void cpuset_css_offline(struct cgroup_subsys_state *css)
{
struct cpuset *cs = css_cs(css);
cpuset_sched_change_begin();
mutex_lock(&cpuset_mutex);
if (is_sched_load_balance(cs))
update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
@ -2056,7 +2049,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
cpuset_dec();
clear_bit(CS_ONLINE, &cs->flags);
cpuset_sched_change_end();
mutex_unlock(&cpuset_mutex);
}
static void cpuset_css_free(struct cgroup_subsys_state *css)