From: Juri Lelli juri.lelli@redhat.com
commit d74b27d63a8bebe2fe634944e4ebdc7b10db7a39 upstream.
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 Signed-off-by: Cai Xinchen caixinchen1@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/cpuset.h | 8 ++++---- kernel/cgroup/cpuset.c | 18 ++++++++++++++---- 2 files changed, 18 insertions(+), 8 deletions(-)
--- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -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); --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -830,8 +830,8 @@ static void rebuild_sched_domains_locked 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 @@ -839,15 +839,13 @@ static void rebuild_sched_domains_locked * 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) @@ -857,9 +855,11 @@ static void rebuild_sched_domains_locked
void rebuild_sched_domains(void) { + get_online_cpus(); mutex_lock(&cpuset_mutex); rebuild_sched_domains_locked(); mutex_unlock(&cpuset_mutex); + put_online_cpus(); }
/** @@ -1617,6 +1617,7 @@ static int cpuset_write_u64(struct cgrou cpuset_filetype_t type = cft->private; int retval = 0;
+ get_online_cpus(); mutex_lock(&cpuset_mutex); if (!is_cpuset_online(cs)) { retval = -ENODEV; @@ -1654,6 +1655,7 @@ static int cpuset_write_u64(struct cgrou } out_unlock: mutex_unlock(&cpuset_mutex); + put_online_cpus(); return retval; }
@@ -1664,6 +1666,7 @@ static int cpuset_write_s64(struct cgrou cpuset_filetype_t type = cft->private; int retval = -ENODEV;
+ get_online_cpus(); mutex_lock(&cpuset_mutex); if (!is_cpuset_online(cs)) goto out_unlock; @@ -1678,6 +1681,7 @@ static int cpuset_write_s64(struct cgrou } out_unlock: mutex_unlock(&cpuset_mutex); + put_online_cpus(); return retval; }
@@ -1716,6 +1720,7 @@ static ssize_t cpuset_write_resmask(stru 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; @@ -1741,6 +1746,7 @@ static ssize_t cpuset_write_resmask(stru 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); @@ -1985,6 +1991,7 @@ static int cpuset_css_online(struct cgro if (!parent) return 0;
+ get_online_cpus(); mutex_lock(&cpuset_mutex);
set_bit(CS_ONLINE, &cs->flags); @@ -2035,6 +2042,7 @@ static int cpuset_css_online(struct cgro spin_unlock_irq(&callback_lock); out_unlock: mutex_unlock(&cpuset_mutex); + put_online_cpus(); return 0; }
@@ -2048,6 +2056,7 @@ static void cpuset_css_offline(struct cg { struct cpuset *cs = css_cs(css);
+ get_online_cpus(); mutex_lock(&cpuset_mutex);
if (is_sched_load_balance(cs)) @@ -2057,6 +2066,7 @@ static void cpuset_css_offline(struct cg clear_bit(CS_ONLINE, &cs->flags);
mutex_unlock(&cpuset_mutex); + put_online_cpus(); }
static void cpuset_css_free(struct cgroup_subsys_state *css)