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 for <linuxppc-dev@lists.ozlabs.org>; Fri,  2 Oct 2015 23:14:49 +1000 (AEST)
Subject: Re: [PATCH v5 08/34] cxlflash: Fix to avoid CXL services during EEH
To: "Matthew R. Ochs" <mrochs@linux.vnet.ibm.com>, linux-scsi@vger.kernel.org,
 James Bottomley <James.Bottomley@HansenPartnership.com>,
 "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
 Brian King <brking@linux.vnet.ibm.com>, Ian Munsie <imunsie@au1.ibm.com>,
 Daniel Axtens <dja@ozlabs.au.ibm.com>,
 Andrew Donnellan <andrew.donnellan@au1.ibm.com>,
 David Laight <David.Laight@ACULAB.COM>
References: <1443714773-9176-1-git-send-email-mrochs@linux.vnet.ibm.com>
 <1443714926-15545-1-git-send-email-mrochs@linux.vnet.ibm.com>
Cc: Michael Neuling <mikey@neuling.org>, linuxppc-dev@lists.ozlabs.org,
 "Manoj N. Kumar" <manoj@linux.vnet.ibm.com>
From: Tomas Henzl <thenzl@redhat.com>
Message-ID: <560E8344.9040608@redhat.com>
Date: Fri, 2 Oct 2015 15:14:44 +0200
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On 1.10.2015 17:55, Matthew R. Ochs wrote:
> During an EEH freeze event, certain CXL services should not be
> called until after the hardware reset has taken place. Doing so
> can result in unnecessary failures and possibly cause other ill
> effects by triggering hardware accesses. This translates to a
> requirement to quiesce all threads that may potentially use CXL
> runtime service during this window. In particular, multiple ioctls
> make use of the CXL services when acting on contexts on behalf of
> the user. Thus, it is essential to 'drain' running ioctls _before_
> proceeding with handling the EEH freeze event.
>
> Create the ability to drain ioctls by wrapping the ioctl handler
> call in a read semaphore and then implementing a small routine that
> obtains the write semaphore, effectively creating a wait point for
> all currently executing ioctls.
>
> Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
> Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
> Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
> Reviewed-by: Daniel Axtens <dja@axtens.net>

Reviewed-by: Tomas Henzl <thenzl@redhat.com>

Tomas