[rt-patch 1/3] arm64/acpi/perf: move pmu allocation to an early CPU up hook

From: Mike Galbraith
Date: Sat Jul 28 2018 - 05:14:11 EST



RT cannot allocate while irqs are disabled.

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974
in_atomic(): 0, irqs_disabled(): 128, pid: 25, name: cpuhp/0
CPU: 0 PID: 25 Comm: cpuhp/0 Not tainted 4.16.18-rt10-rt #2
Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.32 08/22/2017
Call trace:
dump_backtrace+0x0/0x188
show_stack+0x24/0x30
dump_stack+0x9c/0xd0
___might_sleep+0x124/0x188
rt_spin_lock+0x40/0x80
pcpu_alloc+0x104/0x7a0
__alloc_percpu_gfp+0x38/0x48
__armpmu_alloc+0x44/0x168
armpmu_alloc_atomic+0x1c/0x28
arm_pmu_acpi_cpu_starting+0x1cc/0x210
cpuhp_invoke_callback+0xb8/0x820
cpuhp_thread_fun+0xc0/0x1e0
smpboot_thread_fn+0x1ac/0x2c8
kthread+0x134/0x138
ret_from_fork+0x10/0x18

Move the allocation to CPUHP_BP_PREPARE_DYN, where we'll be preemptible,
thus no longer needing GFP_ATOMIC.

Signed-off-by: Mike Galbraith <efault@xxxxxx>
---
drivers/perf/arm_pmu_acpi.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -135,10 +135,10 @@ static struct arm_pmu *arm_pmu_acpi_find
return pmu;
}

- pmu = armpmu_alloc_atomic();
+ pmu = armpmu_alloc();
if (!pmu) {
pr_warn("Unable to allocate PMU for CPU%d\n",
- smp_processor_id());
+ raw_smp_processor_id());
return NULL;
}

@@ -283,7 +283,7 @@ static int arm_pmu_acpi_init(void)
if (ret)
return ret;

- ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_ACPI_STARTING,
+ ret = cpuhp_setup_state(CPUHP_BP_PREPARE_DYN,
"perf/arm/pmu_acpi:starting",
arm_pmu_acpi_cpu_starting, NULL);