| From 75141a770f4f8225d316f6c7e146723a32e9720e Mon Sep 17 00:00:00 2001 |
| From: Jinjie Ruan <ruanjinjie@huawei.com> |
| Date: Fri, 17 Apr 2026 12:01:12 +0800 |
| Subject: ACPI: CPPC: Fix related_cpus inconsistency during CPU hotplug |
| |
| From: Jinjie Ruan <ruanjinjie@huawei.com> |
| |
| commit 75141a770f4f8225d316f6c7e146723a32e9720e upstream. |
| |
| When concurrently bringing up and down two SMT threads of a physical |
| core, many warning call traces occur as below: |
| |
| The issue timeline is as follows: |
| |
| 1. When the system starts, |
| cpufreq: CPU: 220, policy->related_cpus: 220-221, policy->cpus: 220-221 |
| |
| 2. Offline CPU 220 and CPU 221. |
| |
| 3. Online CPU 220 |
| - CPU 221 is now offline, as acpi_get_psd_map() use |
| for_each_online_cpu(), so the cpu_data->shared_cpu_map, |
| policy->cpus, and related_cpus has only CPU 220. |
| |
| cpufreq: CPU: 220, policy->related_cpus: 220, policy->cpus: 220 |
| |
| 4. Offline CPU 220 |
| |
| 5. Online CPU 221, the below call trace occurs: |
| - Since CPU 220 and CPU 221 share one policy, and |
| policy->related_cpus = 220 after step 3, so CPU 221 |
| is not in policy->related_cpus but |
| per_cpu(cpufreq_cpu_data, cpu221) is not NULL. |
| |
| After reverting commit 56eb0c0ed345 ("ACPI: CPPC: Fix remaining |
| for_each_possible_cpu() to use online CPUs"), the issue disappeared. |
| |
| The _PSD (P-State Dependency) defines the hardware-level dependency of |
| frequency control across CPU cores. Since this relationship is a physical |
| attribute of the hardware topology, it remains constant regardless of the |
| online or offline status of the CPUs. |
| |
| Using for_each_online_cpu() in acpi_get_psd_map() is problematic. If a |
| CPU is offline, it will be excluded from the shared_cpu_map. |
| Consequently, if that CPU is brought online later, the kernel will fail |
| to recognize it as part of any shared frequency domain. |
| |
| Switch back to for_each_possible_cpu() to ensure that all cores defined |
| in the ACPI tables are correctly mapped into their respective performance |
| domains from the start. This aligns with the logic of policy->related_cpus, |
| which must encompass all potentially available cores in the domain to |
| prevent logic gaps during CPU hotplug operations. |
| |
| To resolve the original issue regarding the "nosmt" or "nosmt=force" |
| boot parameter, as send_pcc_cmd() function already does if (!desc) |
| continue, so reverting that loop back to for_each_possible_cpu() is ok, |
| only need to change the match_cpc_ptr NULL case in acpi_get_psd_map() to |
| continue as Sean suggested. |
| |
| How to reproduce, on arm64 machine with SMT support which use acpi cppc |
| cpufreq driver: |
| |
| bash test.sh 220 & bash test.sh 221 & |
| |
| The test.sh is as below: |
| while true |
| do |
| echo 0 > /sys/devices/system/cpu/cpu${1}/online |
| sleep 0.5 |
| cat /sys/devices/system/cpu/cpu${1}/cpufreq/related_cpus |
| echo 1 > /sys/devices/system/cpu/cpu${1}/online |
| cat /sys/devices/system/cpu/cpu${1}/cpufreq/related_cpus |
| done |
| |
| CPU: 221 PID: 1119 Comm: cpuhp/221 Kdump: loaded Not tainted 6.6.0debug+ #5 |
| Hardware name: To be filled by O.E.M. S920X20/BC83AMDA01-7270Z, BIOS 20.39 09/04/2024 |
| pstate: a1400009 (NzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) |
| pc : cpufreq_online+0x8ac/0xa90 |
| lr : cpuhp_cpufreq_online+0x18/0x30 |
| sp : ffff80008739bce0 |
| x29: ffff80008739bce0 x28: 0000000000000000 x27: ffff28400ca32200 |
| x26: 0000000000000000 x25: 0000000000000003 x24: ffffd483503ff000 |
| x23: ffffd483504051a0 x22: ffffd48350024a00 x21: 00000000000000dd |
| x20: 000000000000001d x19: ffff28400ca32000 x18: 0000000000000000 |
| x17: 0000000000000020 x16: ffffd4834e6a3fc8 x15: 0000000000000020 |
| x14: 0000000000000008 x13: 0000000000000001 x12: 00000000ffffffff |
| x11: 0000000000000040 x10: ffffd48350430728 x9 : ffffd4834f087c78 |
| x8 : 0000000000000001 x7 : ffff2840092bdf00 x6 : ffffd483504264f0 |
| x5 : ffffd48350405000 x4 : ffff283f7f95cc60 x3 : 0000000000000000 |
| x2 : ffff53bc2f94b000 x1 : 00000000000000dd x0 : 0000000000000000 |
| Call trace: |
| cpufreq_online+0x8ac/0xa90 |
| cpuhp_cpufreq_online+0x18/0x30 |
| cpuhp_invoke_callback+0x128/0x580 |
| cpuhp_thread_fun+0x110/0x1b0 |
| smpboot_thread_fn+0x140/0x190 |
| kthread+0xec/0x100 |
| ret_from_fork+0x10/0x20 |
| ---[ end trace 0000000000000000 ]--- |
| |
| Cc: All applicable <stable@vger.kernel.org> |
| Fixes: 56eb0c0ed345 ("ACPI: CPPC: Fix remaining for_each_possible_cpu() to use online CPUs") |
| Co-developed-by: Sean Kelley <skelley@nvidia.com> |
| Signed-off-by: Sean Kelley <skelley@nvidia.com> |
| Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> |
| [ rjw: Changelog edits ] |
| Link: https://patch.msgid.link/20260417040112.3727756-1-ruanjinjie@huawei.com |
| Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/acpi/cppc_acpi.c | 6 +++--- |
| 1 file changed, 3 insertions(+), 3 deletions(-) |
| |
| --- a/drivers/acpi/cppc_acpi.c |
| +++ b/drivers/acpi/cppc_acpi.c |
| @@ -362,7 +362,7 @@ static int send_pcc_cmd(int pcc_ss_id, u |
| end: |
| if (cmd == CMD_WRITE) { |
| if (unlikely(ret)) { |
| - for_each_online_cpu(i) { |
| + for_each_possible_cpu(i) { |
| struct cpc_desc *desc = per_cpu(cpc_desc_ptr, i); |
| |
| if (!desc) |
| @@ -524,13 +524,13 @@ int acpi_get_psd_map(unsigned int cpu, s |
| else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY) |
| cpu_data->shared_type = CPUFREQ_SHARED_TYPE_ANY; |
| |
| - for_each_online_cpu(i) { |
| + for_each_possible_cpu(i) { |
| if (i == cpu) |
| continue; |
| |
| match_cpc_ptr = per_cpu(cpc_desc_ptr, i); |
| if (!match_cpc_ptr) |
| - goto err_fault; |
| + continue; |
| |
| match_pdomain = &(match_cpc_ptr->domain_info); |
| if (match_pdomain->domain != pdomain->domain) |
