On Thu, Dec 10, 2009 at 1:54 PM, Nagaprabhanjan Bellari
<nagp.knb@xxxxxxxxx> wrote:
> The code snippet is in linux/kernel/softirq.c:__do_softirq():
> ==
> do {
> if (pending & 1) {
> int preempt_count = preempt_count();
> h->action(h);
> if (preempt_count != preempt_count()) {
> printk(KERN_CRIT "BUG: softirq: %p, %x,%x\n",
> h->action, preempt_count, preempt_count());
> dump_crit_stack();
> }
> rcu_bh_qsctr_inc(cpu);
> }
> ==
> What I am trying to understand is the preempt_count check after
> h->action(h); statement. Can somebody tell me why such a prempt_count
> mismatch check is made and why a mismatch is critical?
> Thanks,
> -nagp
What this simply does is that it ensure that the kernel wasn't
preempted anytime before calling h->action(h)
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