[PATCH] x86: kernel irq balance doesn't work
On i386, kernel irq balance doesn't work.
1) In function do_irq_balance, after kernel finds the min_loaded cpu but
before calling set_pending_irq to really pin the selected_irq to the
target cpu, kernel does a cpus_and with irq_affinity[selected_irq].
Later on, when the irq is acked, kernel would calls
move_native_irq=>desc->handler->set_affinity to change the irq affinity.
However, every function pointed by
hw_interrupt_type->set_affinity(unsigned int irq, cpumask_t cpumask)
always changes irq_affinity[irq] to cpumask. Next time when recalling
do_irq_balance, it has to do cpu_ands again with
irq_affinity[selected_irq], but irq_affinity[selected_irq] already
becomes one cpu selected by the first irq balance.
2) Function balance_irq in file arch/i386/kernel/io_apic.c has the same
issue.
[akpm@osdl.org: cleanups]
Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index d03b5ee..afacd6f 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -24,6 +24,8 @@
#ifdef CONFIG_GENERIC_PENDING_IRQ
void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
{
+ set_balance_irq_affinity(irq, mask_val);
+
/*
* Save these away for later use. Re-progam when the
* interrupt is pending
@@ -33,6 +35,7 @@
#else
void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
{
+ set_balance_irq_affinity(irq, mask_val);
irq_affinity[irq] = mask_val;
irq_desc[irq].handler->set_affinity(irq, mask_val);
}