This is a note to let you know that I've just added the patch titled ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: acpi-processor-fix-build-when-config_acpi_processor-m.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From fa26d0c778b432d3d9814ea82552e813b33eeb5c Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Date: Tue, 6 Apr 2021 17:56:40 +0200 Subject: ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> commit fa26d0c778b432d3d9814ea82552e813b33eeb5c upstream. Commit 8cdddd182bd7 ("ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()") tried to fix CPU0 hotplug breakage by copying wakeup_cpu0() + start_cpu0() logic from hlt_play_dead()//mwait_play_dead() into acpi_idle_play_dead(). The problem is that these functions are not exported to modules so when CONFIG_ACPI_PROCESSOR=m build fails. The issue could've been fixed by exporting both wakeup_cpu0()/start_cpu0() (the later from assembly) but it seems putting the whole pattern into a new function and exporting it instead is better. Reported-by: kernel test robot <lkp@xxxxxxxxx> Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()") Cc: <stable@xxxxxxxxxxxxxxx> # 5.10+ Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/smp.h | 2 +- arch/x86/kernel/smpboot.c | 26 ++++++++++++-------------- drivers/acpi/processor_idle.c | 4 +--- 3 files changed, 14 insertions(+), 18 deletions(-) --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -132,7 +132,7 @@ void native_play_dead(void); void play_dead_common(void); void wbinvd_on_cpu(int cpu); int wbinvd_on_all_cpus(void); -bool wakeup_cpu0(void); +void cond_wakeup_cpu0(void); void native_smp_send_reschedule(int cpu); void native_send_call_func_ipi(const struct cpumask *mask); --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1659,13 +1659,17 @@ void play_dead_common(void) local_irq_disable(); } -bool wakeup_cpu0(void) +/** + * cond_wakeup_cpu0 - Wake up CPU0 if needed. + * + * If NMI wants to wake up CPU0, start CPU0. + */ +void cond_wakeup_cpu0(void) { if (smp_processor_id() == 0 && enable_start_cpu0) - return true; - - return false; + start_cpu0(); } +EXPORT_SYMBOL_GPL(cond_wakeup_cpu0); /* * We need to flush the caches before going to sleep, lest we have @@ -1734,11 +1738,8 @@ static inline void mwait_play_dead(void) __monitor(mwait_ptr, 0, 0); mb(); __mwait(eax, 0); - /* - * If NMI wants to wake up CPU0, start CPU0. - */ - if (wakeup_cpu0()) - start_cpu0(); + + cond_wakeup_cpu0(); } } @@ -1749,11 +1750,8 @@ void hlt_play_dead(void) while (1) { native_halt(); - /* - * If NMI wants to wake up CPU0, start CPU0. - */ - if (wakeup_cpu0()) - start_cpu0(); + + cond_wakeup_cpu0(); } } --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -544,9 +544,7 @@ static int acpi_idle_play_dead(struct cp return -ENODEV; #if defined(CONFIG_X86) && defined(CONFIG_HOTPLUG_CPU) - /* If NMI wants to wake up CPU0, start CPU0. */ - if (wakeup_cpu0()) - start_cpu0(); + cond_wakeup_cpu0(); #endif } Patches currently in stable-queue which might be from vkuznets@xxxxxxxxxx are queue-5.11/acpi-processor-fix-build-when-config_acpi_processor-m.patch