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: 17d5c06f7de8 ("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>

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 042fd7e8e03098882b165787b163a597c4c92aa8..f75c4d031eeb2152c75182466dbf5ec97e93c008 100644 (file)
--- 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;
 }