Irq handler reentrancy ?

From: Jean Tourrilhes (jt@bougret.hpl.hp.com)
Date: Wed Sep 04 2002 - 17:18:53 EST


        Hi,

        Just a quick question : can an interrupt handler be preempted
or reenter itself ?
        I know that it can execute in parallel on the various CPUs, so
require spin_lock protection. However, on 2.5.32 I see weird bugs that
lead me to believe that the irq handler is interrupted at the point
where a new hardware interrupt is generated (for example, after
clearing the previous irq or after setting the new irq mask). The box
just freezes, without giving any Opps or anything on the serial
console. Of course, any attempt to add relevant printks make the bug
goes away, so it's impossible to debug.
        2.4.20 runs fine.

        Thanks...

        Jean
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