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: Vincent Donnefort <vincent.donnefort@arm.com>
Suggested-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/YH7r+AoQEReSvxBI@hirez.programming.kicks-ass.net

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 838dcf238f92493425ff585a50c6ad9413ed6df9..e538518556f47da89d52fec50a4419a942200f0d 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -63,6 +63,7 @@ struct cpuhp_cpu_state {
        bool                    rollback;
        bool                    single;
        bool                    bringup;
+       int                     cpu;
        struct hlist_node       *node;
        struct hlist_node       *last;
        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 ret, cnt;
 
-       if (cpu_dying(cpu) != !bringup)
-               set_cpu_dying(cpu, !bringup);
-
        if (st->fail == state) {
                st->fail = CPUHP_INVALID;
                return -EAGAIN;
@@ -467,13 +465,16 @@ static inline enum cpuhp_state
 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 {
        enum cpuhp_state prev_state = st->state;
+       bool bringup = st->state < target;
 
        st->rollback = false;
        st->last = NULL;
 
        st->target = target;
        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;
 }
@@ -481,6 +482,8 @@ cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 static inline void
 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
 {
+       bool bringup = !st->bringup;
+
        st->target = prev_state;
 
        /*
@@ -503,7 +506,9 @@ cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_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 */
@@ -693,6 +698,7 @@ static void cpuhp_create(unsigned int cpu)
 
        init_completion(&st->done_up);
        init_completion(&st->done_down);
+       st->cpu = cpu;
 }
 
 static int cpuhp_should_run(unsigned int cpu)