Re: mmotm 2022-03-16-17-42 uploaded (uml sub-x86_64, sched/fair, RCU)

[Randy Dunlap <rdunlap@infradead.org>]

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Andrew-

On 3/17/22 17:10, Randy Dunlap wrote:
> 
> 
> 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 :(

I took one i386 config file and tested with it:
linux-next 2022-0317 - fails as above
           2022-0216 - fails as above
           2022-0315 - builds successfully

I have 5 i386 configs that fail in this manner and 2 x86_64 configs that fail.
(all from mmotm)

I am attaching the first failing i386 config file but will happily provide
the rest of them if anyone wants them.
(just use 'make oldconfig' and press Enter at any kconfig prompts.)

-- 
~Randy

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