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[PATCH] x86: kernel irq balance doesn't work

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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>
This commit is contained in:
Zhang Yanmin 2006-06-23 02:04:22 -07:00 • committed by Linus Torvalds
parent afa024c3db
commit 1b61b910e9
3 changed files with 31 additions and 11 deletions
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3
kernel/irq/proc.c
View file

@ -24,6 +24,8 @@ static struct proc_dir_entry *smp_affinity_entry[NR_IRQS];
#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 @@ void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
#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);
}