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Subject: Re: [PATCH 4.19 000/219] 4.19.92-stable review
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, shuah@kernel.org, patches@kernelci.org,
        ben.hutchings@codethink.co.uk, lkft-triage@lists.linaro.org,
        stable@vger.kernel.org
References: <20191229162508.458551679@linuxfoundation.org>
 <20191230171959.GC12958@roeck-us.net> <20191230173506.GB1350143@kroah.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <7c5b2866-39d9-5c5f-0282-eef2f34c7fe8@roeck-us.net>
Date:   Tue, 31 Dec 2019 18:01:12 -0800
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On 12/30/19 9:35 AM, Greg Kroah-Hartman wrote:
> On Mon, Dec 30, 2019 at 09:19:59AM -0800, Guenter Roeck wrote:
>> On Sun, Dec 29, 2019 at 06:16:42PM +0100, Greg Kroah-Hartman wrote:
>>> This is the start of the stable review cycle for the 4.19.92 release.
>>> There are 219 patches in this series, all will be posted as a response
>>> to this one.  If anyone has any issues with these being applied, please
>>> let me know.
>>>
>>> Responses should be made by Tue, 31 Dec 2019 16:17:25 +0000.
>>> Anything received after that time might be too late.
>>>
>> Build results:
>> 	total: 156 pass: 141 fail: 15
>> Failed builds:
>> 	i386:tools/perf
>> 	<all mips>
>> 	x86_64:tools/perf
>> Qemu test results:
>> 	total: 381 pass: 316 fail: 65
>> Failed tests:
>> 	<all mips>
>> 	<all ppc64_book3s_defconfig>
>>
>> perf as with v4.14.y.
>>
>> arch/mips/kernel/syscall.c:40:10: fatal error: asm/sync.h: No such file or directory
> 
> Ah, will go drop the offending patch and push out a -rc2 with both of
> these issues fixed.
> 
>> arch/powerpc/include/asm/spinlock.h:56:1: error: type defaults to ‘int’ in declaration of ‘DECLARE_STATIC_KEY_FALSE’
>> and similar errors.
>>
>> The powerpc build problem is inherited from mainline and has not been fixed
>> there as far as I can see. I guess that makes 4.19.y bug-for-bug "compatible"
>> with mainline in that regard.
> 
> bug compatible is fun :(
> 

Not really. It is a terrible idea and results in the opposite of what I would
call a "stable" release.

Anyway, turns out the offending commit is 14c73bd344d ("powerpc/vcpu: Assume
dedicated processors as non-preempt"), which uses static_branch_unlikely().
This function does not exist for ppc in v4.19.y and v5.4.y. Thus, the _impact_
of the error in v4.19.y and v5.4.y is the same as in mainline, but the _cause_
is different. Upstream commit 14c73bd344d should not have been applied to
v4.19.y and v5.4.y and needs to be reverted from those branches.

Guenter