linux-kernel - Re: [PATCH v2 1/7] memcg: memcg_rstat_updated re-entrant safe against irqs

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Message-ID: <2d517f89-3bb4-4de2-8c14-8bb1e4235c7a@suse.cz>
Date: Thu, 15 May 2025 16:57:10 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Shakeel Butt <shakeel.butt@...ux.dev>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>, Alexei Starovoitov <ast@...nel.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Harry Yoo <harry.yoo@...cle.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>,
 bpf@...r.kernel.org, linux-mm@...ck.org, cgroups@...r.kernel.org,
 linux-kernel@...r.kernel.org, Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH v2 1/7] memcg: memcg_rstat_updated re-entrant safe against
 irqs

On 5/15/25 16:31, Shakeel Butt wrote:
> On Thu, May 15, 2025 at 5:47 AM Lorenzo Stoakes
> <lorenzo.stoakes@...cle.com> wrote:
>>
>> Shakeel - This breaks the build in mm-new for me:
>>
>>   CC      mm/pt_reclaim.o
>> In file included from ./arch/x86/include/asm/rmwcc.h:5,
>>                  from ./arch/x86/include/asm/bitops.h:18,
>>                  from ./include/linux/bitops.h:68,
>>                  from ./include/linux/radix-tree.h:11,
>>                  from ./include/linux/idr.h:15,
>>                  from ./include/linux/cgroup-defs.h:13,
>>                  from mm/memcontrol.c:28:
>> mm/memcontrol.c: In function ‘mem_cgroup_alloc’:
>> ./arch/x86/include/asm/percpu.h:39:45: error: expected identifier or ‘(’ before ‘__seg_gs’
>>    39 | #define __percpu_seg_override   CONCATENATE(__seg_, __percpu_seg)
>>       |                                             ^~~~~~
>> ./include/linux/args.h:25:24: note: in definition of macro ‘__CONCAT’
>>    25 | #define __CONCAT(a, b) a ## b
>>       |                        ^
>> ./arch/x86/include/asm/percpu.h:39:33: note: in expansion of macro ‘CONCATENATE’
>>    39 | #define __percpu_seg_override   CONCATENATE(__seg_, __percpu_seg)
>>       |                                 ^~~~~~~~~~~
>> ./arch/x86/include/asm/percpu.h:93:33: note: in expansion of macro ‘__percpu_seg_override’
>>    93 | # define __percpu_qual          __percpu_seg_override
>>       |                                 ^~~~~~~~~~~~~~~~~~~~~
>> ././include/linux/compiler_types.h:60:25: note: in expansion of macro ‘__percpu_qual’
>>    60 | # define __percpu       __percpu_qual BTF_TYPE_TAG(percpu)
>>       |                         ^~~~~~~~~~~~~
>> mm/memcontrol.c:3700:45: note: in expansion of macro ‘__percpu’
>>  3700 |         struct memcg_vmstats_percpu *statc, __percpu *pstatc_pcpu;
>>       |                                             ^~~~~~~~
>> mm/memcontrol.c:3731:25: error: ‘pstatc_pcpu’ undeclared (first use in this function); did you mean ‘kstat_cpu’?
>>  3731 |                         pstatc_pcpu = parent->vmstats_percpu;
>>       |                         ^~~~~~~~~~~
>>       |                         kstat_cpu
>> mm/memcontrol.c:3731:25: note: each undeclared identifier is reported only once for each function it appears in
>>
>> The __percpu macro seems to be a bit screwy with comma-delimited decls, as it
>> seems that putting this on its own line fixes this problem:
>>
> 
> Which compiler (and version) is this? Thanks for the fix.

Hm right I see the same errors with gcc 7, 13, 14, 15 but not with clang.