Re: [Xen-devel] do_softirq + interrupts

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

On Sep 2, 2005, at 3:20 AM, Keir Fraser wrote:
> On 2 Sep 2005, at 00:14, Hollis Blanchard wrote:
>
> > What confuses me is that any other interrupt could come in at point 
> > *** above,
> > right? That interrupt will follow a very similar path, calling 
> > do_softirq
> > again, and handle TIMER_SOFTIRQ. Then when the first do_softirq 
> > resumes, the
> > ASSERT will trip.
> You shouldn't call do_softirq() from nested Xen activations (this is 
> unlike Linux, which is happy to do softirq work from arbitrary 
> interrupt contexts).
Ah ha, this was the tip I needed. The test I had overlooked in 
ret_from_intr was this:
        movl  UREGS_eflags(%esp),%eax
        movb  UREGS_cs(%esp),%al
        testl $(3|X86_EFLAGS_VM),%eax
        jnz   test_all_events
I guess that is cleverly testing both the privilege level being 
returned to and the virtual 8086 mode bit.
Thanks!

--
Hollis Blanchard
IBM Linux Technology Center


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