4.4.2.1 timer中断的应答之ipipe_end

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4.4.2.1 timer中断的应答之ipipe_end

什么时候调用irq_desc.ipipe_end?

1) head domain的中断流控函数，xnintr_irq_handler，如果处理完毕，不再PROPAGATE给root domain，则会调用ipipe_end_irq函数，回调irq_desc->ipipe_end。

2) 假设中断到达了root domain

a. handle_percpu_devid_irq/handle_percpu_irq会显示的调用desc->ipipe_end(desc);

b. handle_fasteoi_irq: 调用cond_release_fasteoi_irq达到了desc->ipipe_end(desc)相同的效果。

针对timer中断，有个奇怪的点：

在__ipipe_ack_hrtimer_irq 已经调用过一次了irq_desc->ipipe_end。

 timer中断到达了root domain handle_percpu_devid_irq/会显示的调用desc->ipipe_end(desc);

这个地方是不是在root域可以省掉一次desc->ipipe_end(desc)？

写了个patch来fix这个问题。在每个时钟中断中，都可以节省一次desc->ipipe_end操作，实际是减少了一次写GIC寄存器。

实测可以正常跑！

diff --git a/include/linux/ipipe_tickdev.h b/include/linux/ipipe_tickdev.h
index 54d1e2daad6e..7906e3d9f301 100644
--- a/include/linux/ipipe_tickdev.h
+++ b/include/linux/ipipe_tickdev.h
@@ -138,6 +138,8 @@ int ipipe_timer_start(void (*tick_handler)(void),
  */
 void ipipe_timer_stop(unsigned cpu);

+bool timer_irq_ipipe_stolen(unsigned int irq);
+
 /*
  * Program the timer
  */
diff --git a/kernel/ipipe/timer.c b/kernel/ipipe/timer.c
index 5354cddb643d..236a81a8d002 100644
--- a/kernel/ipipe/timer.c
+++ b/kernel/ipipe/timer.c
@@ -438,6 +438,26 @@ struct grab_timer_data {
        int retval;
 };

+bool timer_irq_ipipe_stolen(unsigned int irq)
+{
+       struct clock_event_device *evtdev;
+       struct ipipe_timer *timer;
+
+       timer = this_cpu_read(percpu_timer);
+       if (!timer)
+               return false;
+
+       if (!timer->host_timer)
+               return false;
+
+       evtdev = timer->host_timer;
+
+       if(irq == timer->irq && evtdev->ipipe_stolen == 1)
+               return true;
+       else
+               return false;
+}
+
 static void grab_timer(void *arg)
 {
        struct grab_timer_data *data = arg;
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index d4791b5dfe99..412bec17fbc7 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -15,6 +15,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/irqdomain.h>
 #include <linux/ipipe.h>
+#include <linux/ipipe_tickdev.h>

 #include <trace/events/irq.h>

@@ -962,8 +963,10 @@ void handle_percpu_devid_irq(struct irq_desc *desc)
                res = action->handler(irq, raw_cpu_ptr(action->percpu_dev_id));
                trace_irq_handler_exit(irq, action, res);
 #ifdef CONFIG_IPIPE
-               (void)chip;
-               desc->ipipe_end(desc);
+               if(!timer_irq_ipipe_stolen(irq) && desc->ipipe_end){
+                       (void)chip;
+                       desc->ipipe_end(desc);
+               }
                return;
 #endif
        } else {

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