| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Wed, 24 May 2017 10:15:43 +0200 |
| Subject: [PATCH 32/32] cpuhotplug: Link lock stacks for hotplug callbacks |
| |
| The CPU hotplug callbacks are not covered by lockdep versus the cpu hotplug |
| rwsem. |
| |
| CPU0 CPU1 |
| cpuhp_setup_state(STATE, startup, teardown); |
| cpus_read_lock(); |
| invoke_callback_on_ap(); |
| kick_hotplug_thread(ap); |
| wait_for_completion(); hotplug_thread_fn() |
| lock(m); |
| do_stuff(); |
| unlock(m); |
| |
| Lockdep does not know about this dependency and will not trigger on the |
| following code sequence: |
| |
| lock(m); |
| cpus_read_lock(); |
| |
| Add a lockdep map and connect the initiators lock chain with the hotplug |
| thread lock chain, so potential deadlocks can be detected. |
| |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| Acked-by: Ingo Molnar <mingo@kernel.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Sebastian Siewior <bigeasy@linutronix.de> |
| Cc: Steven Rostedt <rostedt@goodmis.org> |
| Link: http://lkml.kernel.org/r/20170524081549.709375845@linutronix.de |
| --- |
| kernel/cpu.c | 13 +++++++++++++ |
| 1 file changed, 13 insertions(+) |
| |
| --- a/kernel/cpu.c |
| +++ b/kernel/cpu.c |
| @@ -66,6 +66,12 @@ struct cpuhp_cpu_state { |
| |
| static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); |
| |
| +#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP) |
| +static struct lock_class_key cpuhp_state_key; |
| +static struct lockdep_map cpuhp_state_lock_map = |
| + STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key); |
| +#endif |
| + |
| /** |
| * cpuhp_step - Hotplug state machine step |
| * @name: Name of the step |
| @@ -415,6 +421,7 @@ static void cpuhp_thread_fun(unsigned in |
| |
| st->should_run = false; |
| |
| + lock_map_acquire(&cpuhp_state_lock_map); |
| /* Single callback invocation for [un]install ? */ |
| if (st->single) { |
| if (st->cb_state < CPUHP_AP_ONLINE) { |
| @@ -441,6 +448,7 @@ static void cpuhp_thread_fun(unsigned in |
| else if (st->state > st->target) |
| ret = cpuhp_ap_offline(cpu, st); |
| } |
| + lock_map_release(&cpuhp_state_lock_map); |
| st->result = ret; |
| complete(&st->done); |
| } |
| @@ -455,6 +463,9 @@ cpuhp_invoke_ap_callback(int cpu, enum c |
| if (!cpu_online(cpu)) |
| return 0; |
| |
| + lock_map_acquire(&cpuhp_state_lock_map); |
| + lock_map_release(&cpuhp_state_lock_map); |
| + |
| /* |
| * If we are up and running, use the hotplug thread. For early calls |
| * we invoke the thread function directly. |
| @@ -498,6 +509,8 @@ static int cpuhp_kick_ap_work(unsigned i |
| enum cpuhp_state state = st->state; |
| |
| trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work); |
| + lock_map_acquire(&cpuhp_state_lock_map); |
| + lock_map_release(&cpuhp_state_lock_map); |
| __cpuhp_kick_ap_work(st); |
| wait_for_completion(&st->done); |
| trace_cpuhp_exit(cpu, st->state, state, st->result); |