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cgroup/cpuset: Change cpuset_rwsem and hotplug lock order

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cpuset_rwsem is going to be acquired from sched_setscheduler() with a
following patch. There are however paths (e.g., spawn_ksoftirqd) in
which sched_scheduler() is eventually called while holding hotplug lock;
this creates a dependecy between hotplug lock (to be always acquired
first) and cpuset_rwsem (to be always acquired after hotplug lock).

Fix paths which currently take the two locks in the wrong order (after
a following patch is applied).

Change-Id: I5589d6cf0f0709bdeb083a08e56d64ebcb90dac9
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bristot@redhat.com
Cc: claudio@evidence.eu.com
Cc: lizefan@huawei.com
Cc: longman@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: mathieu.poirier@linaro.org
Cc: rostedt@goodmis.org
Cc: tj@kernel.org
Cc: tommaso.cucinotta@santannapisa.it
Link: https://lkml.kernel.org/r/20190719140000.31694-7-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Git-commit: d74b27d63a8bebe2fe634944e4ebdc7b10db7a39
[snaseem@codeaurora.org: Resolve trivial merge conflicts and
 change cpuset_mutex and hotplug lock order]
Signed-off-by: Shadab Naseem <snaseem@codeaurora.org>
This commit is contained in:
Juri Lelli 2019-07-19 15:59:58 +02:00 committed by Shadab Naseem
parent 6cbd30c597
commit cd091f5aba
2 changed files with 18 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
include/linux/cpuset.h
View file

@ -40,14 +40,14 @@ static inline bool cpusets_enabled(void)
static inline void cpuset_inc(void)
{
static_branch_inc(&cpusets_pre_enable_key);
static_branch_inc(&cpusets_enabled_key);
static_branch_inc_cpuslocked(&cpusets_pre_enable_key);
static_branch_inc_cpuslocked(&cpusets_enabled_key);
}
static inline void cpuset_dec(void)
{
static_branch_dec(&cpusets_enabled_key);
static_branch_dec(&cpusets_pre_enable_key);
static_branch_dec_cpuslocked(&cpusets_enabled_key);
static_branch_dec_cpuslocked(&cpusets_pre_enable_key);
}
extern int cpuset_init(void);

18
kernel/cgroup/cpuset.c
View file

@ -837,8 +837,8 @@ static void rebuild_sched_domains_locked(void)
cpumask_var_t *doms;
int ndoms;
lockdep_assert_cpus_held();
lockdep_assert_held(&cpuset_mutex);
get_online_cpus();
/*
* We have raced with CPU hotplug. Don't do anything to avoid
@ -846,15 +846,13 @@ static void rebuild_sched_domains_locked(void)
* Anyways, hotplug work item will rebuild sched domains.
*/
if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
goto out;
return;
/* 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_locked(void)
@ -864,9 +862,11 @@ static void rebuild_sched_domains_locked(void)
void rebuild_sched_domains(void)
{
get_online_cpus();
mutex_lock(&cpuset_mutex);
rebuild_sched_domains_locked();
mutex_unlock(&cpuset_mutex);
put_online_cpus();
}
static int update_cpus_allowed(struct cpuset *cs, struct task_struct *p,
@ -1634,6 +1634,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
cpuset_filetype_t type = cft->private;
int retval = 0;
get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) {
retval = -ENODEV;
@ -1671,6 +1672,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
}
out_unlock:
mutex_unlock(&cpuset_mutex);
put_online_cpus();
return retval;
}
@ -1681,6 +1683,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
cpuset_filetype_t type = cft->private;
int retval = -ENODEV;
get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -1695,6 +1698,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
}
out_unlock:
mutex_unlock(&cpuset_mutex);
put_online_cpus();
return retval;
}
@ -1733,6 +1737,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
kernfs_break_active_protection(of->kn);
flush_work(&cpuset_hotplug_work);
get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -1758,6 +1763,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
free_trial_cpuset(trialcs);
out_unlock:
mutex_unlock(&cpuset_mutex);
put_online_cpus();
kernfs_unbreak_active_protection(of->kn);
css_put(&cs->css);
flush_workqueue(cpuset_migrate_mm_wq);
@ -2007,6 +2013,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
if (!parent)
return 0;
get_online_cpus();
mutex_lock(&cpuset_mutex);
set_bit(CS_ONLINE, &cs->flags);
@ -2058,6 +2065,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
spin_unlock_irq(&callback_lock);
out_unlock:
mutex_unlock(&cpuset_mutex);
put_online_cpus();
return 0;
}
@ -2071,6 +2079,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
{
struct cpuset *cs = css_cs(css);
get_online_cpus();
mutex_lock(&cpuset_mutex);
if (is_sched_load_balance(cs))
@ -2080,6 +2089,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
clear_bit(CS_ONLINE, &cs->flags);
mutex_unlock(&cpuset_mutex);
put_online_cpus();
}
static void cpuset_css_free(struct cgroup_subsys_state *css)