linux-kernel - Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5

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Message-Id: <200712101841.30010.fenkes@de.ibm.com>
Date:	Mon, 10 Dec 2007 18:41:29 +0100
From:	Joachim Fenkes <fenkes@...ibm.com>
To:	Roland Dreier <rdreier@...co.com>
Cc:	Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...abs.org,
	LKML <linux-kernel@...r.kernel.org>,
	OF-EWG <ewg@...ts.openfabrics.org>,
	Christoph Raisch <raisch@...ibm.com>,
	Marcus Eder <meder@...ibm.com>,
	OF-General <general@...ts.openfabrics.org>,
	Stefan Roscher <stefan.roscher@...ibm.com>
Subject: Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5

On Monday 10 December 2007 00:22, Roland Dreier wrote:
> Fair enough... according to Documentation/infiniband/core_locking.txt,
> the only driver methods that cannot sleep are:
> 
>     [...]
>     map_phys_fmr

In fact, we do use hCalls there. Our hardware doesn't actually support FMRs,
so we translate a "map FMR" into a "reallocate PMR", which doesn't work
without hCalls. What's more, the hCalls involved (e.g. H_FREE_RESOURCE)
might well return H_LONG_BUSY, so the whole operation might sleep; no way
around it.

How should we deal with this?

Thanks,
  Joachim

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