Re: [RFC][PATCH -rt] irqd starvation on SMP by a single process?

john stultz
2006-05-12T18:04:22Z

On Fri, 2006-05-12 at 07:50 +0200, Ingo Molnar wrote:
> + if (!cpus_equal(current->cpus_allowed, irq_affinity[irq]));
> + set_cpus_allowed(current, irq_affinity[irq]);

Gah! I introduced a terrible bug there.

Note the semi-colon at the end of the if statement! Sorry about that!

The following patch (which I've tested as well) fixes that.

--- 2.6-rt/kernel/irq/manage.c 2006-05-11 18:37:36.000000000 -0500
+++ dev-rt/kernel/irq/manage.c 2006-05-12 12:55:56.000000000 -0500
@@ -724,6 +724,7 @@
set_current_state(TASK_INTERRUPTIBLE);
do_hardirq(desc);
cond_resched_all();
+ local_irq_disable();
__do_softirq();
// do_softirq_from_hardirq();
local_irq_enable();
@@ -731,10 +732,8 @@
/*
* Did IRQ affinities change?
*/
- if (!cpu_isset(smp_processor_id(), irq_affinity[irq])) {
- mask = cpumask_of_cpu(any_online_cpu(irq_affinity[irq]));
- set_cpus_allowed(current, mask);
- }
+ if(!cpus_equal(current->cpus_allowed, irq_affinity[irq]))
+ set_cpus_allowed(current, irq_affinity[irq]);
#endif
schedule();
}