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Re: [Xen-devel] [PATCH v3 1/2] IOMMU/spinlock: Fix a bug found in AMD IOMMU initialization



Hi Quan,

Can I ask a dumb question?

On Wed, Mar 9, 2016 at 8:17 AM, Quan Xu <quan.xu@xxxxxxxxx> wrote:
> pcidevs_lock should be held with interrupt enabled. However there remains
> an exception in AMD IOMMU code, where the lock is acquired with interrupt
> disabled. This inconsistency might lead to deadlock.

Why will this inconsistency lead to deadlock?
I understand the difference between spin_lock_irqsave(), which disable
interrupt,  and spin_lock(), which allows interrupt, however, I didn't
get why misuse the spin_lock_irqsave() at the place of spin_lock()
could potentially lead to a deadlock?
Would you minding pointing me to somewhere I can find the reason or
enlighten me?

Thank you very much!

Best,

Meng

-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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