When booting an arm64 debug kernel with ACPI, I see: BUG: sleeping function called from invalid context at mm/slab.h:420 in_atomic(): 0, irqs_disabled(): 128, pid: 12, name: cpuhp/0 1 lock held by cpuhp/0/12: #0: (cpuhp_state-up){+.+.}, at: [<0000000057aa0dae>] cpuhp_thread_fun+0x13c/0x258 irq event stamp: 28 hardirqs last enabled at (27): [<000000000b861658>] _raw_spin_unlock_irq+0x38/0x58 hardirqs last disabled at (28): [<000000006231cfb1>] cpuhp_thread_fun+0xd0/0x258 softirqs last enabled at (0): [<0000000054d9737a>] copy_process.isra.32.part.33+0x450/0x1480 softirqs last disabled at (0): [< (null)>] (null) CPU: 0 PID: 12 Comm: cpuhp/0 Not tainted 4.15.0+ #18 Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.25 Oct 17 2016 Call trace: dump_backtrace+0x0/0x188 show_stack+0x24/0x2c dump_stack+0xa4/0xe0 ___might_sleep+0x208/0x234 __might_sleep+0x58/0x8c kmem_cache_alloc_trace+0x248/0x3e0 armpmu_alloc+0x38/0x1a8 arm_pmu_acpi_cpu_starting+0x11c/0x15c cpuhp_invoke_callback+0x120/0x100c cpuhp_thread_fun+0xe8/0x258 smpboot_thread_fn+0x170/0x268 kthread+0x110/0x13c ret_from_fork+0x10/0x18
With commit 7d88eb695a1f ("arm/perf: Convert to hotplug state machine"), arm_pmu uses the cpuhotplug framework to initialize the PMU driver when using ACPI. However, the arm_pmu_acpi_cpu_starting() callback comes before CPUHP_AP_ONLINE is reached which means it runs with interrupts diabled and tries to allocate memory with GFP_KERNEL alloc which may sleep. Move CPUHP_AP_PERF_ARM_ACPI_STARTING to come after CPUHP_AP_ONLINE so that the arm_pmu initialization runs with interrupts enabled as it does when booting with device tree. Fixes: 7d88eb695a1f ("arm/perf: Convert to hotplug state machine") Signed-off-by: Mark Salter <msal...@redhat.com> --- include/linux/cpuhotplug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 5172ad0..e07b2da 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -114,7 +114,6 @@ enum cpuhp_state { CPUHP_AP_ARM_VFP_STARTING, CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING, CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING, - CPUHP_AP_PERF_ARM_ACPI_STARTING, CPUHP_AP_PERF_ARM_STARTING, CPUHP_AP_ARM_L2X0_STARTING, CPUHP_AP_ARM_ARCH_TIMER_STARTING, @@ -146,6 +145,7 @@ enum cpuhp_state { CPUHP_AP_SMPBOOT_THREADS, CPUHP_AP_X86_VDSO_VMA_ONLINE, CPUHP_AP_IRQ_AFFINITY_ONLINE, + CPUHP_AP_PERF_ARM_ACPI_STARTING, CPUHP_AP_PERF_ONLINE, CPUHP_AP_PERF_X86_ONLINE, CPUHP_AP_PERF_X86_UNCORE_ONLINE, -- 1.8.3.1