Commit 8eb0984b authored Dec 11, 2015 by Vineet Gupta

ARCv2: intc: Fix random perf irq disabling in SMP setup



As part of fixing another perf issue, observed that after a perf run,
the interrupt got disabled on one/more cores.

Turns out that despite requesting perf irq as percpu, the flow handler
registered was not handle_percpu_irq()

Given that on ARCv2 cores, IRQs < 24 are always private to cpu, we
register the right handler at the very onset.

Before Fix

| [ARCLinux]# cat /proc/interrupts | grep perf
|  20:    0      0      0       0  ARCv2 core Intc  20 ARC perf counters
|
| [ARCLinux]# perf record -c 20000 /sbin/hackbench
| Running with 10*40 (== 400) tasks.
|
| [ARCLinux]# cat /proc/interrupts | grep perf
|  20:    0    522      8    51916  ARCv2 core Intc  20 ARC perf counters
|
| [ARCLinux]# perf record -c 20000 /sbin/hackbench
| Running with 10*40 (== 400) tasks.
|
| [ARCLinux]# cat /proc/interrupts | grep perf
|  20:    0    522      8   104368  ARCv2 core Intc  20 ARC perf counters

After Fix

| [ARCLinux]# cat /proc/interrupts | grep perf
|  20:    0      0      0       0  ARCv2 core Intc  20 ARC perf counters
|
| [ARCLinux]# perf record -c 20000 /sbin/hackbench
| Running with 10*40 (== 400) tasks.
|
| [ARCLinux]# cat /proc/interrupts | grep perf
|  20:  64198  62012  62697  67803  ARCv2 core Intc  20 ARC perf counters
|
| [ARCLinux]# perf record -c 20000 /sbin/hackbench
| Running with 10*40 (== 400) tasks.
|
| [ARCLinux]# cat /proc/interrupts | grep perf
|  20: 126014 122792 123301 133654  ARCv2 core Intc  20 ARC perf counters

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: stable@vger.kernel.org #4.2+
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

parent 6d1a2ade

arch/arc/kernel/intc-arcv2.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -106,10 +106,21 @@ static struct irq_chip arcv2_irq_chip = {
		static int arcv2_irq_map(struct irq_domain *d, unsigned int irq,
		irq_hw_number_t hw)
		{
		if (irq == TIMER0_IRQ \|\| irq == IPI_IRQ)
		/*
		* core intc IRQs [16, 23]:
		* Statically assigned always private-per-core (Timers, WDT, IPI, PCT)
		*/
		if (hw < 24) {
		/*
		* A subsequent request_percpu_irq() fails if percpu_devid is
		* not set. That in turns sets NOAUTOEN, meaning each core needs
		* to call enable_percpu_irq()
		*/
		irq_set_percpu_devid(irq);
		irq_set_chip_and_handler(irq, &arcv2_irq_chip, handle_percpu_irq);
		else
		} else {
		irq_set_chip_and_handler(irq, &arcv2_irq_chip, handle_level_irq);
		}

		return 0;
		}