Hi I have a couple of questions to the kernel code.
I have been trying to fully inderstand (and doccument) the changes in
2.4 wrt. Tasklets and softirq's, BH's and task queues.
In my try to understand how it all works, I came across the code:
(linux/kernel/softirq.c: 246)
static void bh_action(unsigned long nr)
{
int cpu = smp_processor_id();
if (!spin_trylock(&global_bh_lock))
goto resched;
if (!hardirq_trylock(cpu))
goto resched_unlock;
if (bh_base[nr])
bh_base[nr]();
hardirq_endlock(cpu);
spin_unlock(&global_bh_lock);
return;
resched_unlock:
spin_unlock(&global_bh_lock);
resched:
mark_bh(nr);
}
Now all of this but the hardirq_trylock(cpu) and hardirq_endlock(cpu)
makes perfectly sence.
Anyone care to explain the what theese lines do.
Secondly.
Is there a reason why to implement a queue (TASKLET_HI) for the old
BH's, instead of just using a single tasklet for all BH administraton.
Would'ent this guarentee that no BH is executed at the same time, and at
the same time reduce code complexity, and remove the global_bh_lock?
TIA
Anders Fugmann
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