[PATCHv2 2/2] arm-cci: fix PMU interrupt flags

[Mark Rutland]

Currently the IRQ core is permitted to make the CCI PMU IRQ handler
threaded, and will allow userspace to change the CPU affinity of the
interrupt behind our back. Both of these could violate our
synchronisation requirements with the core perf code, which relies upon
strict CPU affinity and disabling of interrupts to guarantee mutual
exclusion in some cases.

As with the CPU PMU drivers, we should request the interrupt with
IRQF_NOBALANCING and IRQF_NO_THREAD, to avoid these issues. At the same
time, we drop IRQF_SHARED. The interrupt is not shared in practice, and
the driver detects and skips duplicate IRQs at probe time, so it is not
necessary.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Marc Zyngier <marc.zyngier at arm.com>
Cc: Punit Agrawal <punit.agrawal at arm.com>
Cc: Suzuki K Poulose <suzuki.poulose at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Olof Johansson <olof at lixom.net>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: <arm at kernel.org>
---
 drivers/bus/arm-cci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
index a49b283..ffce9e3 100644
--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -881,7 +881,8 @@ static int pmu_request_irq(struct cci_pmu *cci_pmu, irq_handler_t handler)
 	 * This should allow handling of non-unique interrupt for the counters.
 	 */
 	for (i = 0; i < cci_pmu->nr_irqs; i++) {
-		int err = request_irq(cci_pmu->irqs[i], handler, IRQF_SHARED,
+		int err = request_irq(cci_pmu->irqs[i], handler,
+				IRQF_NOBALANCING | IRQF_NO_THREAD,
 				"arm-cci-pmu", cci_pmu);
 		if (err) {
 			dev_err(&pmu_device->dev, "unable to request IRQ%d for ARM CCI PMU counters\n",
-- 
1.9.1