irqbalance seg faults with 2.6.38 or later kernels [patch + solution included] if running under Xen hypervisor

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

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The reason behind it is that irqbalance parses the /proc/interrupts
and whenever it hits something it can't understand:

 RES:  191614137   73904910    Rescheduling interrupts

It will count the number of interrupts towards the IRQ 0. That IRQ does exist
when the kernel boots under baremetal:

  0:         46          0       IO-APIC-edge      timer

but under Xen, the timer interrupts are initialized much later:

 272:   41197188          0        xen-percpu-virq      timer0

and the first IRQ that is used is not zero, but rather one:

   1:      73037          0          0          0          0          0  xen-pirq-ioapic-edge  i8042

so when irqbalance tries to account for the IRQ 'RES' to the IRQ 0
it fails and segfaults. The attached patch fixes it for whoever else is
hitting this problem. I am not sure who the upstream maintainer is for this so
I am sending this patch to the different distros as well.


--- irqbalance-0.56.orig/procinterrupts.c	2010-06-10 10:45:55.000000000 -0400
+++ irqbalance-0.56/procinterrupts.c	2011-05-10 20:22:06.897465003 -0400
@@ -50,7 +50,7 @@ void parse_proc_interrupts(void)
 		int cpunr;
 		int	 number;
 		uint64_t count;
-		char *c, *c2;
+		char *c, *c2, *err;
 
 		if (getline(&line, &size, file)==0)
 			break;
@@ -64,7 +64,11 @@ void parse_proc_interrupts(void)
 			continue;
 		*c = 0;
 		c++;
-		number = strtoul(line, NULL, 10);
+		number = strtoul(line, &err, 10);
+		/* Man page says that if that happens and number == 0, then it
+		 * failed to parse. */
+		if (err == line && number == 0)
+			continue;
 		count = 0;
 		cpunr = 0;
 

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--- irqbalance-0.56.orig/procinterrupts.c	2010-06-10 10:45:55.000000000 -0400
+++ irqbalance-0.56/procinterrupts.c	2011-05-10 20:22:06.897465003 -0400
@@ -50,7 +50,7 @@ void parse_proc_interrupts(void)
 		int cpunr;
 		int	 number;
 		uint64_t count;
-		char *c, *c2;
+		char *c, *c2, *err;
 
 		if (getline(&line, &size, file)==0)
 			break;
@@ -64,7 +64,11 @@ void parse_proc_interrupts(void)
 			continue;
 		*c = 0;
 		c++;
-		number = strtoul(line, NULL, 10);
+		number = strtoul(line, &err, 10);
+		/* Man page says that if that happens and number == 0, then it
+		 * failed to parse. */
+		if (err == line && number == 0)
+			continue;
 		count = 0;
 		cpunr = 0;
 

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