From: George Dunlap <George.Dunlap@eu.citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Keir Fraser <keir.xen@gmail.com>
Subject: Re: Interrupt code cleanup [RFC]
Date: Thu, 1 Sep 2011 10:03:37 +0100 [thread overview]
Message-ID: <CAFLBxZZW+hrxJVkSwnWDkmpT33oZQkxS5E+EfnTeVpw6Tg+Bag@mail.gmail.com> (raw)
In-Reply-To: <4E5E58AD.9060500@citrix.com>
On Wed, Aug 31, 2011 at 4:52 PM, Andrew Cooper
<andrew.cooper3@citrix.com> wrote:
> Are there any areas people have noticed where the irq code is limited
> and could be improved?
The locking seems a bit strange too, and doesn't seem to be documented
anywhere. For instance, in irq.c:__clear_irq_vector(),
cfg->move_in_progress is protected by vector_lock. But in
io_apic.c:send_cleanup_vector(), cfg->move_in_progress is read without
any locks, and cfg->move_cleanup_count is written without any locks,
or any memory barriers; but in smp_irq_move_cleanup_interrupt(),
cfg->move_cleanup_count is protected by desc->lock.
It may be that this is all OK and carefully thought out, but it's a
bit hard to believe. And even if it were carefully thought out, if
it's not either obvious or documented, at some point someone will make
a change that breaks the delicately balanced invariants.
I'm taking a look at that now...
-George
prev parent reply other threads:[~2011-09-01 9:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-31 15:52 Interrupt code cleanup [RFC] Andrew Cooper
2011-09-01 9:03 ` George Dunlap [this message]
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