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Subject: Re: [PATCH 4/4] powerpc/xive: prepare all hcalls to support long busy
 delays
To: Michael Ellerman <mpe@ellerman.id.au>,
 Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 linuxppc-dev@lists.ozlabs.org
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 <87d0yb8zye.fsf@concordia.ellerman.id.au>
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From: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@kaod.org>
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Date: Mon, 7 May 2018 09:32:57 +0200
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On 05/07/2018 04:30 AM, Michael Ellerman wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
>> On Fri, 2018-05-04 at 20:42 +1000, Michael Ellerman wrote:
>>> Cédric Le Goater <clg@kaod.org> writes:
>>>
>>>> This is not the case for the moment, but future releases of pHyp might
>>>> need to introduce some synchronisation routines under the hood which
>>>> would make the XIVE hcalls longer to complete.
>>>>
>>>> As this was done for H_INT_RESET, let's wrap the other hcalls in a
>>>> loop catching the H_LONG_BUSY_* codes.
>>>
>>> Are we sure it's safe to msleep() in all these paths?
>>
>> Probably not. We can have the IRQ descriptor lock. We might need to
>> mdelay.
>>
>> There's a Kconfig option (forgot which one) that will add checks for
>> attempts to sleep inside locks, you should run with that.
> 
> CONFIG_DEBUG_ATOMIC_SLEEP

[  435.757986] kexec_core: Starting new kernel
[  435.778162] BUG: scheduling while atomic: kexec/1633/0x00000003

That proved to be useful. Thanks.

I will resend the full series changing msleep() to mdelay() and fixing
a bit the changelog.

Cheers,

C.