smp/hotplug: Differentiate the AP-work lockdep class between up and down

With lockdep-crossrelease we get deadlock reports that span cpu-up and
cpu-down chains. Such deadlocks cannot possibly happen because cpu-up
and cpu-down are globally serialized.

  CPU0                  CPU1                    CPU2
  cpuhp_up_callbacks:   takedown_cpu:           cpuhp_thread_fun:

  cpuhp_state
                        irq_lock_sparse()
    irq_lock_sparse()
                        wait_for_completion()
                                                cpuhp_state
                                                complete()

Now that we have consistent AP state, we can trivially separate the
AP-work class between up and down using st->bringup.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: max.byungchul.park@gmail.com
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Link: https://lkml.kernel.org/r/20170920170546.922524234@infradead.org

diff --git a/kernel/cpu.c b/kernel/cpu.c
index d6f1b8c364009e15899dd92a158d4f846e9ec27f..d5c09985fbb64cff970a805b7ee20e33759ce178 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -68,9 +68,26 @@ 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);
+static struct lockdep_map cpuhp_state_up_map =
+       STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
+static struct lockdep_map cpuhp_state_down_map =
+       STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
+
+
+static void inline cpuhp_lock_acquire(bool bringup)
+{
+       lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+
+static void inline cpuhp_lock_release(bool bringup)
+{
+       lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+#else
+
+static void inline cpuhp_lock_acquire(bool bringup) { }
+static void inline cpuhp_lock_release(bool bringup) { }
+
 #endif
 
 /**
@@ -486,7 +503,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
        if (WARN_ON_ONCE(!st->should_run))
                return;
 
-       lock_map_acquire(&cpuhp_state_lock_map);
+       cpuhp_lock_acquire(bringup);
 
        if (st->single) {
                state = st->cb_state;
@@ -537,7 +554,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
        }
 
 next:
-       lock_map_release(&cpuhp_state_lock_map);
+       cpuhp_lock_release(bringup);
 
        if (!st->should_run)
                complete(&st->done);
@@ -554,8 +571,11 @@ cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
        if (!cpu_online(cpu))
                return 0;
 
-       lock_map_acquire(&cpuhp_state_lock_map);
-       lock_map_release(&cpuhp_state_lock_map);
+       cpuhp_lock_acquire(false);
+       cpuhp_lock_release(false);
+
+       cpuhp_lock_acquire(true);
+       cpuhp_lock_release(true);
 
        /*
         * If we are up and running, use the hotplug thread. For early calls
@@ -593,8 +613,11 @@ static int cpuhp_kick_ap_work(unsigned int cpu)
        enum cpuhp_state prev_state = st->state;
        int ret;
 
-       lock_map_acquire(&cpuhp_state_lock_map);
-       lock_map_release(&cpuhp_state_lock_map);
+       cpuhp_lock_acquire(false);
+       cpuhp_lock_release(false);
+
+       cpuhp_lock_acquire(true);
+       cpuhp_lock_release(true);
 
        trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
        ret = cpuhp_kick_ap(st, st->target);