RE: [patch V2 38/38] x86/smpboot/64: Implement arch_cpuhp_init_parallel_bringup() and enable it

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

On Sat, May 06 2023 at 00:53, Michael Kelley wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Sent: Thursday, May 4, 2023 12:03 
> PM
> [snip]
>
>> @@ -934,10 +961,10 @@ static void announce_cpu(int cpu, int ap
>>      if (!node_width)
>>              node_width = num_digits(num_possible_nodes()) + 1; /* + '#' */
>> 
>> -    if (cpu == 1)
>> -            printk(KERN_INFO "x86: Booting SMP configuration:\n");
>> -
>>      if (system_state < SYSTEM_RUNNING) {
>> +            if (num_online_cpus() == 1)
>
> Unfortunately, this new check doesn't work.  Here's the output I get:
>
> [    0.721384] smp: Bringing up secondary CPUs ...
> [    0.725359] smpboot: x86: Booting SMP configuration:
> [    0.729249] .... node  #0, CPUs:        #2
> [    0.729654] smpboot: x86: Booting SMP configuration:
> [    0.737247]       #4
>
> Evidently num_online_cpus() isn't updated until after all the primary
> siblings get started.

Duh. Where is that brown paperbag?

> When booting with cpuhp.parallel=0, the output is good.

Exactly that was on the command line when I quickly booted that change :(

The below should fix it for real.

Thanks,

        tglx
---
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -951,9 +951,9 @@ static int wakeup_secondary_cpu_via_init
 /* reduce the number of lines printed when booting a large cpu count system */
 static void announce_cpu(int cpu, int apicid)
 {
+       static int width, node_width, first = 1;
        static int current_node = NUMA_NO_NODE;
        int node = early_cpu_to_node(cpu);
-       static int width, node_width;
 
        if (!width)
                width = num_digits(num_possible_cpus()) + 1; /* + '#' sign */
@@ -962,7 +962,7 @@ static void announce_cpu(int cpu, int ap
                node_width = num_digits(num_possible_nodes()) + 1; /* + '#' */
 
        if (system_state < SYSTEM_RUNNING) {
-               if (num_online_cpus() == 1)
+               if (first)
                        pr_info("x86: Booting SMP configuration:\n");
 
                if (node != current_node) {
@@ -975,11 +975,11 @@ static void announce_cpu(int cpu, int ap
                }
 
                /* Add padding for the BSP */
-               if (num_online_cpus() == 1)
+               if (first)
                        pr_cont("%*s", width + 1, " ");
+               first = 0;
 
                pr_cont("%*s#%d", width - num_digits(cpu), " ", cpu);
-
        } else
                pr_info("Booting Node %d Processor %d APIC 0x%x\n",
                        node, cpu, apicid);