[Xen-devel] [question] will softirq handler potentially be called many times?

[Kai Huang <mail.kai.huang@xxxxxxxxx>]

Hi,

I see the __do_softirq is called when ! in_atomic(), which means
potentially __do_softirq may be interrupted by trap, exception,
interrupt, etc, so seems softirq handler may be executed many times?

For example, if interrupt happens after i =
find_first_set_bit(pending), the same softirq hander will be called
twice as the do_softriq will be called after all interrupt handler
returned, and the pending bit has not been cleared yet when first
do_softirq was called.

static void __do_softirq(unsigned long ignore_mask)
{
    ......
    for ( ; ; )
    {
        ......
        i = find_first_set_bit(pending);
                                                   <- interrupt happens
        clear_bit(i, &softirq_pending(cpu));
        (*softirq_handlers[i])();
    }
}

-cody

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