[PATCH 6.6 148/299] Revert "parisc: Only list existing CPUs in cpu_possible_mask"

Greg Kroah-Hartman
2024-02-27T13:53:36Z

From: Helge Deller <deller@gmx.de>

commit 82b143aeb169b8b55798d7d2063032e1a6ceeeb0 upstream.

This reverts commit 0921244f6f4f0d05698b953fe632a99b38907226.

It broke CPU hotplugging because it modifies the __cpu_possible_mask
after bootup, so that it will be different than nr_cpu_ids, which
then effictively breaks the workqueue setup code and triggers crashes
when shutting down CPUs at runtime.

Guenter was the first who noticed the wrong values in __cpu_possible_mask,
since the cpumask Kunit tests were failig.

Reverting this commit fixes both issues, but sadly brings back this
uncritical runtime warning:
register_cpu_capacity_sysctl: too early to get CPU4 device!

Signed-off-by: Helge Deller <deller@gmx.de>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lkml.org/lkml/2024/2/4/146
Link: https://lore.kernel.org/lkml/Zb0mbHlIud_bqftx@slm.duckdns.org/t/
Cc: stable@vger.kernel.org # 6.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/parisc/kernel/processor.c | 8 --------
1 file changed, 8 deletions(-)

--- a/arch/parisc/kernel/processor.c
+++ b/arch/parisc/kernel/processor.c
@@ -172,7 +172,6 @@ static int __init processor_probe(struct
p->cpu_num = cpu_info.cpu_num;
p->cpu_loc = cpu_info.cpu_loc;

- set_cpu_possible(cpuid, true);
store_cpu_topology(cpuid);

#ifdef CONFIG_SMP
@@ -474,13 +473,6 @@ static struct parisc_driver cpu_driver _
*/
void __init processor_init(void)
{
- unsigned int cpu;
-
reset_cpu_topology();
-
- /* reset possible mask. We will mark those which are possible. */
- for_each_possible_cpu(cpu)
- set_cpu_possible(cpu, false);
-
register_parisc_driver(&cpu_driver);
}