MIPS: loongson64: add IRQ work based on self-IPI

Since the commit 91840be8f710 ("irq_work: Fix use-after-free in
irq_work_single() on PREEMPT_RT"), we observed the performance of
execve() is significantly impacted on MIPS.

While we are unsure how that commit caused the impact or how to improve
it (or even if it can be improved at all), implementing IRQ work with
self-IPI seems able to mitigate the impaction.

Perhaps this can/should be implemented for other MIPS architecture
processors as well, but we don't have the enough knowledge of them, nor
access to the hardware.  So only implement it for loongson64 here.

Link: https://lore.kernel.org/6be1cdd5f91dd7418a32ff372a6f3ae259b19195.camel@xry111.site/
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/mips/loongson64/smp.c b/arch/mips/loongson64/smp.c
index 147acd972a07..e584299d0fde 100644
--- a/arch/mips/loongson64/smp.c
+++ b/arch/mips/loongson64/smp.c
@@ -381,6 +381,13 @@ loongson3_send_ipi_mask(const struct cpumask *mask, unsigned int action)
 		ipi_write_action(cpu_logical_map(i), (u32)action);
 }
 
+#ifdef CONFIG_IRQ_WORK
+void arch_irq_work_raise(void)
+{
+	loongson3_send_ipi_single(smp_processor_id(), SMP_IRQ_WORK);
+}
+#endif
+
 static irqreturn_t loongson3_ipi_interrupt(int irq, void *dev_id)
 {
 	int cpu = smp_processor_id();
@@ -397,6 +404,9 @@ static irqreturn_t loongson3_ipi_interrupt(int irq, void *dev_id)
 		irq_exit();
 	}
 
+	if (action & SMP_IRQ_WORK)
+		irq_work_run();
+
 	return IRQ_HANDLED;
 }