From d74b27d63a8bebe2fe634944e4ebdc7b10db7a39 Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Fri, 19 Jul 2019 15:59:58 +0200 Subject: [PATCH] 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 Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- include/linux/cpuset.h | 8 ++++---- kernel/cgroup/cpuset.c | 22 +++++++++++++++++----- 2 files changed, 21 insertions(+), 9 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 934633a05d20..7f1478c26a33 100644 --- 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); diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index e1a8d168c5e9..5c5014caa23c 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -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)