linux-kernel - Re: [PATCH v6 02/10] slab: add opt-in caching layer of percpu sheaves

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Message-ID: <e58c8482-bd11-4111-b912-daf8b43ebb15@suse.cz>
Date: Thu, 28 Aug 2025 10:01:39 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Thorsten Leemhuis <linux@...mhuis.info>,
 Suren Baghdasaryan <surenb@...gle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>,
 Harry Yoo <harry.yoo@...cle.com>, Uladzislau Rezki <urezki@...il.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
 maple-tree@...ts.infradead.org,
 Linux Next Mailing List <linux-next@...r.kernel.org>,
 Stephen Rothwell <sfr@...b.auug.org.au>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH v6 02/10] slab: add opt-in caching layer of percpu sheaves

On 8/28/25 09:43, Thorsten Leemhuis wrote:
> On 27.08.25 10:26, Vlastimil Babka wrote:
>> Specifying a non-zero value for a new struct kmem_cache_args field
>> sheaf_capacity will setup a caching layer of percpu arrays called
>> sheaves of given capacity for the created cache.
>> 
>> Allocations from the cache will allocate via the percpu sheaves (main or
>> spare) as long as they have no NUMA node preference. Frees will also
>> put the object back into one of the sheaves.
>> [...]
> 
> This patch showed up in linux-next today and from a *quick* glance at
> things I suspect it might be the reason why my daily next rpm builds for
> Fedora failed today like this:

Hi, thanks for the report.
> ""
> In file included from ./include/linux/spinlock.h:63,
>                  from ./include/linux/mmzone.h:8,
>                  from ./include/linux/gfp.h:7,
>                  from ./include/linux/mm.h:7,
>                  from mm/slub.c:13:
> mm/slub.c: In function ‘__pcs_replace_empty_main’:
> mm/slub.c:4727:64: error: ‘local_trylock_t’ {aka ‘__seg_gs struct spinlock’} has no member named ‘llock’; did you mean ‘lock’?
>  4727 |         lockdep_assert_held(this_cpu_ptr(&s->cpu_sheaves->lock.llock));
>       |                                                                ^~~~~
> ./include/linux/lockdep.h:392:61: note: in definition of macro ‘lockdep_assert_held’
>   392 | #define lockdep_assert_held(l)                  do { (void)(l); } while (0)
>       |                                                             ^
> [...]
> mm/slub.c:5653:29: note: in expansion of macro ‘this_cpu_ptr’
>  5653 |         lockdep_assert_held(this_cpu_ptr(&s->cpu_sheaves->lock.llock));
>       |                             ^~~~~~~~~~~~
> make[3]: *** [scripts/Makefile.build:287: mm/slub.o] Error 1
> make[2]: *** [scripts/Makefile.build:556: mm] Error 2
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [/builddir/build/BUILD/kernel-6.17.0-build/kernel-next-20250828/linux-6.17.0-0.0.next.20250828.432.vanilla.fc44.x86_64/Makefile:2017: .] Error 2
> make: *** [Makefile:256: __sub-make] Error 2
> ""
> 
> Full log: https://download.copr.fedorainfracloud.org/results/@kernel-vanilla/next/fedora-rawhide-x86_64/09498568-next-next-all/builder-live.log.gz

Oh so I assume the .config here has both LOCKDEP and PREEMPT_RT?
I tried to make lockdep_assert_held() with trylock but forgot about the RT
difference. The solution is Alexei's patch

https://lore.kernel.org/all/20250718021646.73353-2-
alexei.starovoitov@...il.com/

Wonder if I can just fast-track it to here from that series?