[PATCH] arm_pmu: Use disable_irq_nosync when disabling SPI in CPU teardown hook

[Will Deacon]

Commit 6de3f79112cc ("arm_pmu: explicitly enable/disable SPIs at hotplug")
moved all of the arm_pmu IRQ enable/disable calls to the CPU hotplug hooks,
regardless of whether they are implemented as PPIs or SPIs. This can
lead to us sleeping from atomic context due to disable_irq blocking:

 | BUG: sleeping function called from invalid context at kernel/irq/manage.c:112
 | in_atomic(): 1, irqs_disabled(): 128, pid: 15, name: migration/1
 | no locks held by migration/1/15.
 | irq event stamp: 192
 | hardirqs last  enabled at (191): [<00000000803c2507>]
 | _raw_spin_unlock_irq+0x2c/0x4c
 | hardirqs last disabled at (192): [<000000007f57ad28>] multi_cpu_stop+0x9c/0x140
 | softirqs last  enabled at (0): [<0000000004ee1b58>]
 | copy_process.isra.77.part.78+0x43c/0x1504
 | softirqs last disabled at (0): [<          (null)>]           (null)
 | CPU: 1 PID: 15 Comm: migration/1 Not tainted 4.16.0-rc3-salvator-x #1651
 | Hardware name: Renesas Salvator-X board based on r8a7796 (DT)
 | Call trace:
 |  dump_backtrace+0x0/0x140
 |  show_stack+0x14/0x1c
 |  dump_stack+0xb4/0xf0
 |  ___might_sleep+0x1fc/0x218
 |  __might_sleep+0x70/0x80
 |  synchronize_irq+0x40/0xa8
 |  disable_irq+0x20/0x2c
 |  arm_perf_teardown_cpu+0x80/0xac

Since the interrupt is always CPU-affine and this code is running with
interrupts disabled, we can just use disable_irq_nosync as we know there
isn't a concurrent invocation of the handler to worry about.

Reported-by: Geert Uytterhoeven <geert at linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert+renesas at glider.be>
Acked-by: Acked-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
 drivers/perf/arm_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 0c2ed11c0603..f63db346c219 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -638,7 +638,7 @@ static int arm_perf_teardown_cpu(unsigned int cpu, struct hlist_node *node)
 		if (irq_is_percpu_devid(irq))
 			disable_percpu_irq(irq);
 		else
-			disable_irq(irq);
+			disable_irq_nosync(irq);
 	}
 
 	per_cpu(cpu_armpmu, cpu) = NULL;
-- 
2.1.4