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Date:   Thu, 17 Mar 2022 17:10:29 -0700
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Subject: Re: mmotm 2022-03-16-17-42 uploaded (uml sub-x86_64, sched/fair, RCU)
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To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     broonie@kernel.org, mhocko@suse.cz, sfr@canb.auug.org.au,
        linux-next@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        mm-commits@vger.kernel.org,
        linux-um <linux-um@lists.infradead.org>, paulmck@kernel.org,
        Richard Weinberger <richard@nod.at>,
        Johannes Berg <johannes@sipsolutions.net>
References: <20220317004304.95F89C340E9@smtp.kernel.org>
 <0f622499-36e1-ea43-ddc3-a8b3bb08d34b@infradead.org>
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 <917e9ce0-c8cf-61b2-d1ba-ebf25bbd979d@infradead.org>
 <20220317165100.2755c5ae6a3a08b7ecb06181@linux-foundation.org>
From:   Randy Dunlap <rdunlap@infradead.org>
In-Reply-To: <20220317165100.2755c5ae6a3a08b7ecb06181@linux-foundation.org>
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On 3/17/22 16:51, Andrew Morton wrote:
> On Wed, 16 Mar 2022 21:52:44 -0700 Randy Dunlap <rdunlap@infradead.org> wrote:
> 
>>>> In file included from ./arch/x86/include/generated/asm/rwonce.h:1:0,
>>>>                  from ../include/linux/compiler.h:248,
>>>>                  from ../include/linux/kernel.h:20,
>>>>                  from ../include/linux/cpumask.h:10,
>>>>                  from ../include/linux/energy_model.h:4,
>>>>                  from ../kernel/sched/fair.c:23:
>>>> ../include/linux/psi.h: In function ‘cgroup_move_task’:
>>>> ../include/linux/rcupdate.h:414:36: error: dereferencing pointer to incomplete type ‘struct css_set’
>>>>  #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
>>>>                                     ^~~~
>>>
>>> Works For Me.  I tried `make x86_64_defconfig' and `make i386_defconfig' too.
>>>
>>> Can you please share that .config, or debug a bit?
>>
>> $ make ARCH=um SUBARCH=x86_64 defconfig
>>
> 
> I still can't reproduce this :(
> 
>> This fixes the build error for me when CONFIG_PSI=n.
> 
> I have CONFIG_PSI=n

There was also this report about linux-next, also with CONFIG_PSI=n:

https://lore.kernel.org/all/EF33D230-9A8F-41C5-A38D-95128603224F@linux.ibm.com/

but I just tried to build with the .config file supplied there and didn't
have any build errors...

If it was just me & mmotm, I could see it being a problem with applying
patches, but this other report looks the same as my initial report.

I dunno. If it persists, we will track it down and quash it.

>> ---
>>  include/linux/psi.h |    3 +++
>>  1 file changed, 3 insertions(+)
>>
>> --- mmotm-2022-0316-1742.orig/include/linux/psi.h
>> +++ mmotm-2022-0316-1742/include/linux/psi.h
>> @@ -53,6 +53,9 @@ static inline int psi_cgroup_alloc(struc
>>  static inline void psi_cgroup_free(struct cgroup *cgrp)
>>  {
>>  }
>> +
>> +#include <linux/cgroup-defs.h>
>> +
>>  static inline void cgroup_move_task(struct task_struct *p, struct css_set *to)
>>  {
>>  	rcu_assign_pointer(p->cgroups, to);
> 
> Nothing in -next touches psi.h so I am unable to determine which patch
> needs fixing :(

-- 
~Randy