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Commit 5f4b55e1 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
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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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas 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
parent 724a8688

kernel/cpu.c

+32 −9
Original line number Diff line number Diff line
@@ -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);