Re: [patch V4 33/37] cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

On Mon, May 22 2023 at 23:27, Mark Brown wrote:
> On Mon, May 22, 2023 at 11:04:17PM +0200, Thomas Gleixner wrote:
>
>> That does not make any sense at all and my tired brain does not help
>> either.
>
>> Can you please apply the below debug patch and provide the output?
>
> Here's the log, a quick glance says the 
>
>       if (!--ncpus)
>               break;
>
> check is doing the wrong thing

Obviously.

Let me find a brown paperbag and go to sleep before I even try to
compile the obvious fix.

---
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 005f863a3d2b..88a7ede322bd 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1770,9 +1770,6 @@ static void __init cpuhp_bringup_mask(const struct 
cpumask *mask, unsigned int n
        for_each_cpu(cpu, mask) {
                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 
-               if (!--ncpus)
-                       break;
-
                if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
                        /*
                         * If this failed then cpu_up() might have only
@@ -1781,6 +1778,9 @@ static void __init cpuhp_bringup_mask(const struct 
cpumask *mask, unsigned int n
                         */
                        WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, 
CPUHP_OFFLINE));
                }
+
+               if (!--ncpus)
+                       break;
        }
 }