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

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Message-ID: <1532769235.5926.0.camel@gmx.de>
Date:   Sat, 28 Jul 2018 11:13:55 +0200
From:   Mike Galbraith <efault@....de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [rt-patch 1/3] arm64/acpi/perf: move pmu allocation to an early CPU
 up hook


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@....de>
---
 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);