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Subject: Re: [PATCH 1/2] cxl: Keep IRQ mappings on context teardown
To: Michael Neuling <mikey@neuling.org>, mpe@ellerman.id.au
References: <1461301069-12331-1-git-send-email-mikey@neuling.org>
Cc: Joerg-Stephan Vogt <JSVOGT@de.ibm.com>,
 Frederic Barrat <frederic.barrat@fr.ibm.com>,
 Vaibhav Jain <vaibhav@linux.vnet.ibm.com>,
 Wolfgang Bolz1 <Wolfgang.Bolz@de.ibm.com>, imunsie@au1.ibm.com,
 Frank Haverkamp <HAVERKAM@de.ibm.com>, linuxppc-dev@lists.ozlabs.org
From: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
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Date: Fri, 22 Apr 2016 15:14:14 +1000
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On 22/04/16 14:57, Michael Neuling wrote:
> Keep IRQ mappings on context teardown.  This won't leak IRQs as if we
> allocate the mapping again, the generic code will give the same
> mapping used last time.
>
> Doing this works around a race in the generic code. Masking the
> interrupt introduces a race which can crash the kernel or result in
> IRQ that is never EOIed. The lost of EOI results in all subsequent
> mappings to the same HW IRQ never receiving an interrupt.
>
> We've seen this race with cxl test cases which are doing heavy context
> startup and teardown at the same time as heavy interrupt load.
>
> A fix to the generic code is being investigated also.
>
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> cc: stable@vger.kernel.org # 3.8

Tested on top of 4.6-rc3 using the genwqe-echo test utility[0].

Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

[0] 
https://github.com/ibm-genwqe/genwqe-user/blob/master/tools/genwqe_echo.c

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited