ARCv2: perf: Ensure perf intr gets enabled on all cores
authorVineet Gupta <vgupta@synopsys.com>
Fri, 11 Dec 2015 07:43:12 +0000 (13:13 +0530)
committerVineet Gupta <vgupta@synopsys.com>
Sat, 12 Dec 2015 10:33:59 +0000 (16:03 +0530)
This was the second perf intr issue

perf sampling on multicore requires intr to be enabled on all cores.
ARC perf probe code used helper arc_request_percpu_irq() which calls
 - request_percpu_irq() on core0
 - enable_percpu_irq() on all all cores (including core0)

genirq requires that request be made ahead of enable call.
However if perf probe happened on non core0 (observed on a 3.18 kernel),
enable would get called ahead of request, failing obviously and
rendering perf intr disabled on all such cores

[   11.120000] 1 ARC perf       : 8 counters (48 bits), 113 conditions, [overflow IRQ support]
[   11.130000] 1 -----> enable_percpu_irq() IRQ 20 failed
[   11.140000] 3 -----> enable_percpu_irq() IRQ 20 failed
[   11.140000] 2 -----> enable_percpu_irq() IRQ 20 failed
[   11.140000] 0 =====> request_percpu_irq() IRQ 20
[   11.140000] 0 -----> enable_percpu_irq() IRQ 20

Fix this fragility, by calling request_percpu_irq() on whatever core
calls probe (there is no requirement on which core calls this anyways)
and then calling enable on each cores.

Interestingly this started as invesigation of STAR 9000838902:
"sporadically IRQs enabled on perf prob"

which was about occassional boot spew as request_percpu_irq got called
non-locally (from an IPI), and re-enabled interrupts in following path
proc_mkdir ->  spin_unlock_irq()

which the irq work code didn't like.

| ARC perf     : 8 counters (48 bits), 113 conditions, [overflow IRQ support]
|
| BUG: failure at ../kernel/irq_work.c:135/irq_work_run_list()!
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.18.10-01127-g285efb8e66d1 #2
|
| Stack Trace:
|  arc_unwind_core.constprop.1+0x94/0x104
|  dump_stack+0x62/0x98
|  irq_work_run_list+0xb0/0xb4
|  irq_work_run+0x22/0x3c
|  do_IPI+0x74/0x9c
|  handle_irq_event_percpu+0x34/0x164
|  handle_percpu_irq+0x58/0x78
|  generic_handle_irq+0x1e/0x2c
|  arch_do_IRQ+0x3c/0x60
|  ret_from_exception+0x0/0x8

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

index 0c08bb1ce15aab114c344609879eaa86bfa59a9d..8b134cfe5e1f11023b559639497f7e1a35d2ee79 100644 (file)
@@ -428,12 +428,11 @@ static irqreturn_t arc_pmu_intr(int irq, void *dev)
 
 #endif /* CONFIG_ISA_ARCV2 */
 
-void arc_cpu_pmu_irq_init(void)
+static void arc_cpu_pmu_irq_init(void *data)
 {
-       struct arc_pmu_cpu *pmu_cpu = this_cpu_ptr(&arc_pmu_cpu);
+       int irq = *(int *)data;
 
-       arc_request_percpu_irq(arc_pmu->irq, smp_processor_id(), arc_pmu_intr,
-                              "ARC perf counters", pmu_cpu);
+       enable_percpu_irq(irq, IRQ_TYPE_NONE);
 
        /* Clear all pending interrupt flags */
        write_aux_reg(ARC_REG_PCT_INT_ACT, 0xffffffff);
@@ -515,7 +514,6 @@ static int arc_pmu_device_probe(struct platform_device *pdev)
 
        if (has_interrupts) {
                int irq = platform_get_irq(pdev, 0);
-               unsigned long flags;
 
                if (irq < 0) {
                        pr_err("Cannot get IRQ number for the platform\n");
@@ -524,24 +522,12 @@ static int arc_pmu_device_probe(struct platform_device *pdev)
 
                arc_pmu->irq = irq;
 
-               /*
-                * arc_cpu_pmu_irq_init() needs to be called on all cores for
-                * their respective local PMU.
-                * However we use opencoded on_each_cpu() to ensure it is called
-                * on core0 first, so that arc_request_percpu_irq() sets up
-                * AUTOEN etc. Otherwise enable_percpu_irq() fails to enable
-                * perf IRQ on non master cores.
-                * see arc_request_percpu_irq()
-                */
-               preempt_disable();
-               local_irq_save(flags);
-               arc_cpu_pmu_irq_init();
-               local_irq_restore(flags);
-               smp_call_function((smp_call_func_t)arc_cpu_pmu_irq_init, 0, 1);
-               preempt_enable();
-
-               /* Clean all pending interrupt flags */
-               write_aux_reg(ARC_REG_PCT_INT_ACT, 0xffffffff);
+               /* intc map function ensures irq_set_percpu_devid() called */
+               request_percpu_irq(irq, arc_pmu_intr, "ARC perf counters",
+                                  this_cpu_ptr(&arc_pmu_cpu));
+
+               on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1);
+
        } else
                arc_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;