RE: [PATCH v4] trace,x86: add x86 irq vector tracepoints

[Seiji Aguchi]

Hi,

> ... except the cost can be reduced to zero *AND* be made into a more general 
> mechanism by simply hooking the IDT.

Thank you for giving me the comment.
In my understanding,  we can introduce a more general mechanism by sandwiching 
an existing handler between tracepoints.
The pseudo code is like this:

@@ -17,7 +18,7 @@ static void default_threshold_interrupt(void)
 
 void (*mce_threshold_vector)(void) = default_threshold_interrupt;
 
-asmlinkage void smp_threshold_interrupt(void)
+static void do_smp_threshold_interrupt(void)
 {
        irq_enter();
        exit_idle();
@@ -27,3 +28,10 @@ asmlinkage void smp_threshold_interrupt(void)
        /* Ack only at the end to avoid potential reentry */
        ack_APIC_irq();
 }
+
+asmlinkage void smp_threshold_interrupt(void) {
+       trace_arch_irq_vector_entry(THRESHOLD_APIC_VECTOR);
+       do_smp_threshold_interrupt();
+       trace_arch_irq_vector_exit(THRESHOLD_APIC_VECTOR);
+}

If I misunderstand something, please let me know.

Seiji