Hello.
I can't understand the preempt_count() check in irq_exit()
and local_bh_enable(). Did you meant irq_count() instead?
I beleive preempt_disable() should not disable soft interrupts.
In local_bh_enable() it is probably unneeded at all, because
nested local_bh_disable() is rare (i think), and do_softirq()
checks in_interrupt().
Now suppose preempt_count() & PREEMPT_MASK == 0.
Then local_bh_enable() has a small preemptible window between
__local_bh_enable() and do_softirq()->local_irq_save(flags).
It is only latency problem.
But in irq_exit() case interrupt context may be preempted
while doing wakeup_softirqd(cpu) after __local_bh_enable()
in do_softirq().
So i suggest something like this pseudo code:
__preempt_hack(offset)
{
barrier();
preempt_count() -= offset
#ifdef CONFIG_PREEMPT
- 1
#endif
;
}
irq_exit()
{
__preempt_hack(HARDIRQ_OFFSET);
if (unlikely(!irq_count() &&
softirq_pending(smp_processor_id())))
do_softirq();
preempt_enable_no_resched();
}
local_bh_enable()
{
__preempt_hack(SOFTIRQ_OFFSET);
if (unlikely(!irq_count() &&
softirq_pending(smp_processor_id())))
do_softirq();
preempt_enable();
}
Or just add extra preempt_disable() in both functions to kill
terrible __preempt_hack().
Sorry, i have no remove-irqlock patches applied, so can't
suggest diff.
Oleg.
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This archive was generated by hypermail 2b29 : Tue Jul 23 2002 - 22:00:45 EST