Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5ebe7742 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

smp/hotplug: Differentiate the AP completion 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.

  takedown_cpu()
    irq_lock_sparse()
    wait_for_completion(&st->done)

                                cpuhp_thread_fun
                                  cpuhp_up_callback
                                    cpuhp_invoke_callback
                                      irq_affinity_online_cpu
                                        irq_local_spare()
                                        irq_unlock_sparse()
                                  complete(&st->done)

Now that we have consistent AP state, we can trivially separate the
AP completion 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>
Acked-by: default avatar <max.byungchul.park@gmail.com>
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Link: https://lkml.kernel.org/r/20170920170546.872472799@infradead.org
parent 5f4b55e1

kernel/cpu.c

+32 −17
Original line number Diff line number Diff line
@@ -46,7 +46,8 @@ 
 * @bringup:	Single callback bringup or teardown selector

 * @cb_state:	The state for a single callback (install/uninstall)

 * @result:	Result of the operation

 * @done:	Signal completion to the issuer of the task

 * @done_up:	Signal completion to the issuer of the task for cpu-up

 * @done_down:	Signal completion to the issuer of the task for cpu-down

 */

struct cpuhp_cpu_state {

	enum cpuhp_state	state;
@@ -61,7 +62,8 @@ struct cpuhp_cpu_state { 
	struct hlist_node	*last;

	enum cpuhp_state	cb_state;

	int			result;

	struct completion	done;

	struct completion	done_up;

	struct completion	done_down;

#endif

};
@@ -130,14 +132,6 @@ static bool cpuhp_is_ap_state(enum cpuhp_state state) 
	return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;

}



/*

 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.

 */

static bool cpuhp_is_atomic_state(enum cpuhp_state state)

{

	return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;

}



static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)

{

	struct cpuhp_step *sp;
@@ -232,6 +226,26 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, 
}



#ifdef CONFIG_SMP

static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)

{

	struct completion *done = bringup ? &st->done_up : &st->done_down;

	wait_for_completion(done);

}



static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)

{

	struct completion *done = bringup ? &st->done_up : &st->done_down;

	complete(done);

}



/*

 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.

 */

static bool cpuhp_is_atomic_state(enum cpuhp_state state)

{

	return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;

}



/* Serializes the updates to cpu_online_mask, cpu_present_mask */

static DEFINE_MUTEX(cpu_add_remove_lock);

bool cpuhp_tasks_frozen;
@@ -368,7 +382,7 @@ static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st) 
	smp_mb();

	st->should_run = true;

	wake_up_process(st->thread);

	wait_for_completion(&st->done);

	wait_for_ap_thread(st, st->bringup);

}



static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
@@ -391,7 +405,7 @@ static int bringup_wait_for_ap(unsigned int cpu) 
	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);



	/* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */

	wait_for_completion(&st->done);

	wait_for_ap_thread(st, true);

	if (WARN_ON_ONCE((!cpu_online(cpu))))

		return -ECANCELED;
@@ -464,7 +478,8 @@ static void cpuhp_create(unsigned int cpu) 
{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);



	init_completion(&st->done);

	init_completion(&st->done_up);

	init_completion(&st->done_down);

}



static int cpuhp_should_run(unsigned int cpu)
@@ -557,7 +572,7 @@ static void cpuhp_thread_fun(unsigned int cpu) 
	cpuhp_lock_release(bringup);



	if (!st->should_run)

		complete(&st->done);

		complete_ap_thread(st, bringup);

}



/* Invoke a single callback on a remote cpu */
@@ -753,7 +768,7 @@ static int takedown_cpu(unsigned int cpu) 
	 *

	 * Wait for the stop thread to go away.

	 */

	wait_for_completion(&st->done);

	wait_for_ap_thread(st, false);

	BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);



	/* Interrupts are moved away from the dying cpu, reenable alloc/free */
@@ -772,7 +787,7 @@ static void cpuhp_complete_idle_dead(void *arg) 
{

	struct cpuhp_cpu_state *st = arg;



	complete(&st->done);

	complete_ap_thread(st, false);

}



void cpuhp_report_idle_dead(void)
@@ -939,7 +954,7 @@ void cpuhp_online_idle(enum cpuhp_state state) 
		return;



	st->state = CPUHP_AP_ONLINE_IDLE;

	complete(&st->done);

	complete_ap_thread(st, true);

}



/* Requires cpu_add_remove_lock to be held */