[PATCH RFC] irq: Set CPU affinity as soon as the irq thread is created

[Sankara Muthukrishnan <sankara.m@xxxxxxxxx>]

Hi there,

As irq_thread_check_affinity is called inside the while loop in the
IRQ thread, the core affinity is set only when an interrupt happens.
It does not seem to be a bad idea to set the core affinity soon after
the thread is created also (as shown in the patch).
irq_thread_check_affinity calls kmalloc_node that can sleep. In an
embedded target where IRQ affinities are pre-configured during
boot-time (and not modified through /proc/irq/../smp_affinity) during
run-time, the extra latency due to irq_thread_check_affinity can be
avoided during processing of the first interrupt with this patch.
Thoughts?

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 87dc053..bf2cdc2 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -791,6 +791,7 @@ static int irq_thread(void *data)

        sched_setscheduler(current, SCHED_FIFO, &param);
        current->irqaction = action;
+       irq_thread_check_affinity(desc, action);

        while (!irq_wait_for_interrupt(action)) {

- Sankara
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