smp/hotplug: Undo tglxs brainfart

The attempt to prevent overwriting an active state resulted in a
disaster which effectively disables all dynamically allocated hotplug
states.

Cleanup the mess.

Fixes: dc280d936239 ("cpu/hotplug: Prevent overwriting of callbacks")
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 042fd7e8e030..f75c4d031eeb 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1471,6 +1471,7 @@ int __cpuhp_setup_state(enum cpuhp_state state,
                         bool multi_instance)
 {
         int cpu, ret = 0;
+        bool dynstate;
 
         if (cpuhp_cb_check(state) || !name)
                 return -EINVAL;
@@ -1480,6 +1481,12 @@ int __cpuhp_setup_state(enum cpuhp_state state,
         ret = cpuhp_store_callbacks(state, name, startup, teardown,
                                     multi_instance);
 
+        dynstate = state == CPUHP_AP_ONLINE_DYN;
+        if (ret > 0 && dynstate) {
+                state = ret;
+                ret = 0;
+        }
+
         if (ret || !invoke || !startup)
                 goto out;
 
@@ -1508,7 +1515,7 @@ out:
          * If the requested state is CPUHP_AP_ONLINE_DYN, return the
          * dynamically allocated state in case of success.
          */
-        if (!ret && state == CPUHP_AP_ONLINE_DYN)
+        if (!ret && dynstate)
                 return state;
         return ret;
 }