[PATCH] powerpc/64: Fix latency tracing for lazy irq replay

[PATCH] powerpc/64: Fix latency tracing for lazy irq replay

[Nicholas Piggin]

When returning from an exception to a soft-enabled context, pending
IRQs are replayed but IRQ tracing is not reset, so a number of them
can get chained together into the same IRQ-disabled trace.

Fix this by having __check_irq_replay re-set IRQ trace. This is
conceptually where we respond to the next interrupt, so it fits the
semantics of the IRQ tracer.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/irq.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index efbadcbbf694..df18085de8c4 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -138,6 +138,13 @@ notrace unsigned int __check_irq_replay(void)
 	 */
 	unsigned char happened = local_paca->irq_happened;
 
+	/*
+	 * We are responding to the next interrupt, so interrupt-off
+	 * latencies should be reset here.
+	 */
+	trace_hardirqs_on();
+	trace_hardirqs_off();
+
 	if (happened & PACA_IRQ_HARD_DIS) {
 		/* Clear bit 0 which we wouldn't clear otherwise */
 		local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
@@ -292,6 +299,7 @@ notrace void arch_local_irq_restore(unsigned long en)
 #endif /* CONFIG_TRACE_IRQFLAGS */
 
 	soft_disable_set(IRQS_DISABLED);
+	trace_hardirqs_off();
 
 	/*
 	 * Check if anything needs to be re-emitted. We haven't
@@ -301,6 +309,7 @@ notrace void arch_local_irq_restore(unsigned long en)
 	replay = __check_irq_replay();
 
 	/* We can soft-enable now */
+	trace_hardirqs_on();
 	soft_disable_set(IRQS_ENABLED);
 
 	/*
-- 
2.13.3

Re: powerpc/64: Fix latency tracing for lazy irq replay

[Michael Ellerman]

On Sat, 2017-10-21 at 07:56:06 UTC, Nicholas Piggin wrote:
> When returning from an exception to a soft-enabled context, pending
> IRQs are replayed but IRQ tracing is not reset, so a number of them
> can get chained together into the same IRQ-disabled trace.
> 
> Fix this by having __check_irq_replay re-set IRQ trace. This is
> conceptually where we respond to the next interrupt, so it fits the
> semantics of the IRQ tracer.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/ff967900c9d4740f6337c6456f1111

cheers