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cgroup/cpuset: Change cpuset_rwsem and hotplug lock order 

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).

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>
This commit is contained in:
Juri Lelli 2019-07-19 15:59:58 +02:00 committed by Ingo Molnar
parent 1243dc518c
commit d74b27d63a
2 changed files with 21 additions and 9 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);

22
kernel/cgroup/cpuset.c
View File

@ -973,8 +973,8 @@ static void rebuild_sched_domains_locked(void)
cpumask_var_t *doms;
int ndoms;
lockdep_assert_cpus_held();
percpu_rwsem_assert_held(&cpuset_rwsem);
get_online_cpus();
/*
* We have raced with CPU hotplug. Don't do anything to avoid
@ -983,19 +983,17 @@ static void rebuild_sched_domains_locked(void)
*/
if (!top_cpuset.nr_subparts_cpus &&
!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
goto out;
return;
if (top_cpuset.nr_subparts_cpus &&
!cpumask_subset(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_and_rebuild_sched_domains(ndoms, doms, attr);
out:
put_online_cpus();
}
#else /* !CONFIG_SMP */
static void rebuild_sched_domains_locked(void)
@ -1005,9 +1003,11 @@ static void rebuild_sched_domains_locked(void)
void rebuild_sched_domains(void)
{
get_online_cpus();
percpu_down_write(&cpuset_rwsem);
rebuild_sched_domains_locked();
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
}
/**
@ -2245,6 +2245,7 @@ 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();
percpu_down_write(&cpuset_rwsem);
if (!is_cpuset_online(cs)) {
retval = -ENODEV;
@ -2282,6 +2283,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
}
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
return retval;
}
@ -2292,6 +2294,7 @@ 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();
percpu_down_write(&cpuset_rwsem);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -2306,6 +2309,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
}
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
return retval;
}
@ -2344,6 +2348,7 @@ 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();
percpu_down_write(&cpuset_rwsem);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -2369,6 +2374,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
free_cpuset(trialcs);
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
kernfs_unbreak_active_protection(of->kn);
css_put(&cs->css);
flush_workqueue(cpuset_migrate_mm_wq);
@ -2499,6 +2505,7 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
return -EINVAL;
css_get(&cs->css);
get_online_cpus();
percpu_down_write(&cpuset_rwsem);
if (!is_cpuset_online(cs))
goto out_unlock;
@ -2506,6 +2513,7 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
retval = update_prstate(cs, val);
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
css_put(&cs->css);
return retval ?: nbytes;
}
@ -2711,6 +2719,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
if (!parent)
return 0;
get_online_cpus();
percpu_down_write(&cpuset_rwsem);
set_bit(CS_ONLINE, &cs->flags);
@ -2763,6 +2772,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
spin_unlock_irq(&callback_lock);
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
return 0;
}
@ -2781,6 +2791,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
{
struct cpuset *cs = css_cs(css);
get_online_cpus();
percpu_down_write(&cpuset_rwsem);
if (is_partition_root(cs))
@ -2801,6 +2812,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
clear_bit(CS_ONLINE, &cs->flags);
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
}
static void cpuset_css_free(struct cgroup_subsys_state *css)