[ltt-dev] [BUG] [PATCH] LTTV - interrupt handler time calculation is wrong in case of nested interrupts

[Gaurav Singh]

Hi all,

I was using the interrupt handler plugin and noticed that sometimes
the timer interrupt  handler was taking a lot of time. Specifically
the max time indicated by the plugin was wrong. This was because the
time calculated by the plugin in case of nested interrupts is wrong.

Nested interrupt:
Interrupt 1 (entry)  .... 1
Interrupt 2(entry).....2
Interrupt 2 (exit) ..... 3
Interrupt 3 (exit) ..... 4

The plugin did the following calculation:
Time for 1st interrupt = timeat (3) - timeat (1)
Time for 2nd interrupt = timeat (4) - timeat (2)


The following patch corrects this anamoly. Basically it takes the up
the most recent interrupt and pairs the irq_exit with it. Please check
if this works for you.

diff -uprN lttv-0.10.0-pre11-10032008/lttv/modules/gui/interrupts/interrupts.c
../lttv-0.10.0-pre11-10032008/lttv/modules/gui/interrupts/interrupts.c
--- lttv-0.10.0-pre11-10032008/lttv/modules/gui/interrupts/interrupts.c
2007-10-16 06:44:40.000000000 +0530
+++ ../lttv-0.10.0-pre11-10032008/lttv/modules/gui/interrupts/interrupts.c
     2008-09-29 15:13:02.000000000 +0530
@@ -583,7 +583,7 @@ static void CalculateData(LttTime time_e
   LttTime duration;
   GArray *FirstRequestIrqExit = event_data->FirstRequestIrqExit;
   GArray *FirstRequestIrqEntry = event_data->FirstRequestIrqEntry;
-  for(i = 0; i < FirstRequestIrqEntry->len; i++)
+  for(i = FirstRequestIrqEntry->len-1; i >=0; i--)
   {
     element = &g_array_index(FirstRequestIrqEntry,irq_entry,i);
     if(element->cpu_id == cpu_id)



Regards,
Gaurav