Commit 2ea46c6f authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

cpumask/hotplug: Fix cpu_dying() state tracking 



Vincent reported that for states with a NULL startup/teardown function
we do not call cpuhp_invoke_callback() (because there is none) and as
such we'll not update the cpu_dying() state.

The stale cpu_dying() can eventually lead to triggering BUG().

Rectify this by updating cpu_dying() in the exact same places the
hotplug machinery tracks its directional state, namely
cpuhp_set_state() and cpuhp_reset_state().

Reported-by: default avatarVincent Donnefort <vincent.donnefort@arm.com>
Suggested-by: default avatarVincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarVincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/YH7r+AoQEReSvxBI@hirez.programming.kicks-ass.net
parent 3a7956e2

kernel/cpu.c

+11 −5
Original line number Original line Diff line number Diff line
@@ -63,6 +63,7 @@ struct cpuhp_cpu_state { 
	bool			rollback;

	bool			rollback;

	bool			single;

	bool			single;

	bool			bringup;

	bool			bringup;

	int			cpu;

	struct hlist_node	*node;

	struct hlist_node	*node;

	struct hlist_node	*last;

	struct hlist_node	*last;

	enum cpuhp_state	cb_state;

	enum cpuhp_state	cb_state;
@@ -160,9 +161,6 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, 
	int (*cb)(unsigned int cpu);

	int (*cb)(unsigned int cpu);

	int ret, cnt;

	int ret, cnt;





	if (cpu_dying(cpu) != !bringup)

		set_cpu_dying(cpu, !bringup);



	if (st->fail == state) {

	if (st->fail == state) {

		st->fail = CPUHP_INVALID;

		st->fail = CPUHP_INVALID;

		return -EAGAIN;

		return -EAGAIN;
@@ -467,13 +465,16 @@ static inline enum cpuhp_state 
cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)

cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)

{

{

	enum cpuhp_state prev_state = st->state;

	enum cpuhp_state prev_state = st->state;

	bool bringup = st->state < target;





	st->rollback = false;

	st->rollback = false;

	st->last = NULL;

	st->last = NULL;





	st->target = target;

	st->target = target;

	st->single = false;

	st->single = false;

	st->bringup = st->state < target;

	st->bringup = bringup;

	if (cpu_dying(st->cpu) != !bringup)

		set_cpu_dying(st->cpu, !bringup);





	return prev_state;

	return prev_state;

}

}
@@ -481,6 +482,8 @@ cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target) 
static inline void

static inline void

cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)

cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)

{

{

	bool bringup = !st->bringup;



	st->target = prev_state;

	st->target = prev_state;





	/*

	/*
@@ -503,7 +506,9 @@ cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state) 
			st->state++;

			st->state++;

	}

	}





	st->bringup = !st->bringup;

	st->bringup = bringup;

	if (cpu_dying(st->cpu) != !bringup)

		set_cpu_dying(st->cpu, !bringup);

}

}





/* Regular hotplug invocation of the AP hotplug thread */

/* Regular hotplug invocation of the AP hotplug thread */
@@ -693,6 +698,7 @@ static void cpuhp_create(unsigned int cpu) 




	init_completion(&st->done_up);

	init_completion(&st->done_up);

	init_completion(&st->done_down);

	init_completion(&st->done_down);

	st->cpu = cpu;

}

}





static int cpuhp_should_run(unsigned int cpu)

static int cpuhp_should_run(unsigned int cpu)