Re: [Xen-devel] map_domain_page_global() and interrupts

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

!in_irq() because the function is not reentrant.

local_irq_is_enabled() because the function uses flush_tlb_all() which must
be able to IPI remote CPUs.  We mustn't have them stuck spinning on
globalmap_lock with interrupts disabled -- that would result in deadlock.

 -- Keir

On 29/7/07 01:02, "Andrew Gallagher" <ajcg@xxxxxxxxxxx> wrote:

> In the file xen/arch/x86/x86_32/domain_page.c, the
> map_domain_page_global function has the following assertion:
> ASSERT(!in_irq() && local_irq_is_enabled()).  This assertion is followed
> by use of a spin lock without disabling then reenabling irqs.
> 
> The assertion that the function is not called from an interrupted context
> seems to flag this function as not interrupt safe.  Why is this?  Is the
> use of the IOREMAP_VIRT not interrupt safe itself.  The only reason this
> seems to be not interrupt safe is becuase of the use of a spinlock without
> disabling and reenabling irqs.
> 
> My question is that, if interrupts are disabled then reenabled before and
> after acquiring and releasing the spinlock, is it then ok to call this
> function from the context of an interrupt?
> 
> Thanks,
> Andrew
> 
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