From: Julien Grall <julien.grall@linaro.org>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: Oleksandr Tyshchenko <oleksandr.tyshchenko@globallogic.com>,
stefano.stabellini@eu.citrix.com, tim@xen.org,
xen-devel@lists.xen.org
Subject: Re: [PATCH v2] xen: arm: increase priority of SGIs used as IPIs
Date: Mon, 17 Mar 2014 12:11:11 +0000 [thread overview]
Message-ID: <5326E65F.5050101@linaro.org> (raw)
In-Reply-To: <1395055862-23455-1-git-send-email-ian.campbell@citrix.com>
Hi Ian,
On 03/17/2014 11:31 AM, Ian Campbell wrote:
> Code such as on_selected_cpus expects/requires that an IPI can preempt a
> processor which is just handling a normal interrupt. Lacking this property can
> result in a deadlock between two CPUs trying to IPI each other from interrupt
> context.
>
> For the time being there is only two priorities, IRQ and IPI, although it is
> also conceivable that in the future some IPIs might be higher priority than
> others. This could be used to implement a better BUG() than we have now, but I
> haven't tackled that yet.
>
> Tested with a debug patch which sends a local IPI from a keyhandler, which is
> run in serial interrupt context.
>
> This should also fix the issue reported by Oleksandr in "xen/arm:
> maintenance_interrupt SMP fix" without resorting to trylock.
Sorry, I didn't notice it before. If you plan to keep the last
paragraph, can you add a link to the patch?
Regards,
--
Julien Grall
next prev parent reply other threads:[~2014-03-17 12:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-17 11:31 [PATCH v2] xen: arm: increase priority of SGIs used as IPIs Ian Campbell
2014-03-17 12:11 ` Julien Grall [this message]
2014-03-17 12:20 ` Ian Campbell
2014-03-17 12:59 ` Ian Campbell
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