Re: [PATCH v2 2/5] perf: arm_cspmu: Support shared interrupts

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Hi Robin,

On Thu, 1 Jun 2023, Robin Murphy wrote:
On 2023-06-01 04:01, Ilkka Koskinen wrote:
Some of the PMUs may share the interrupt. Support them by
setting IRQF_SHARED

This has the usual problem of allowing any PMU instance to move the IRQ affinity to a different CPU without also migrating all the other PMU contexts, and thus breaking perf core's assumptions of mutual exclusion.

I see, I wasn't aware of such an assumption. Sounds like there isn't necessarily an easy and clean solution for the shared interrupt case. I drop the patch and get back on the issue if we come up with something reasonable later.

Cheers, Ilkka


Thanks,
Robin.

Signed-off-by: Ilkka Koskinen <ilkka@xxxxxxxxxxxxxxxxxxxxxx>
---
  drivers/perf/arm_cspmu/arm_cspmu.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
index 88547a2b73e6..cc5204d1b5fb 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.c
+++ b/drivers/perf/arm_cspmu/arm_cspmu.c
@@ -1067,8 +1067,8 @@ static int arm_cspmu_request_irq(struct arm_cspmu *cspmu)
  		return irq;
    	ret = devm_request_irq(dev, irq, arm_cspmu_handle_irq,
- IRQF_NOBALANCING | IRQF_NO_THREAD, dev_name(dev),
-			       cspmu);
+ IRQF_NOBALANCING | IRQF_NO_THREAD | IRQF_SHARED,
+			       dev_name(dev), cspmu);
  	if (ret) {
  		dev_err(dev, "Could not request IRQ %d\n", irq);
  		return ret;




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