From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andres Lagar-Cavilla <andreslc@cs.toronto.edu>
Subject: Re: do_iret bug in xen
Date: Tue, 27 Nov 2007 16:50:35 -0500
Message-ID: <474C912B.2040401@cs.toronto.edu>
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Cc: ashish.bijlani@gmail.com, Daniel Stodden <stodden@cs.tum.edu>
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raise_softirq is not the same as actually doing it. Raise only sets a 
bit indicating pending softirq. Before returning to the guest, the bin 
triggers actual execution of the softirq

Andres

    since "sti" is on, an interrupt can occur which can cause the
    control to enter "__runq_tickle", which then invokes
    "cpumask_raise_softirq(mask, SCHEDULE_SOFTIRQ)" to send IPI to a
    processor causing the control to enter "__enter_scheduler" which
    changes the current.