linux-kernel - Re: [OFFLIST PATCH 2/2] cgroup: use subsystem-specific rstat locks to avoid contention

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Message-ID: <gzwa67k6i35jw5h3qfdajuzxa2zgm6ws2x5rjiisont4xiz4bp@kneusjz5bxwb>
Date: Thu, 22 May 2025 00:23:44 +0200
From: Klara Modin <klarasmodin@...il.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Tejun Heo <tj@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Alexei Starovoitov <ast@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Yosry Ahmed <yosry.ahmed@...ux.dev>, 
	Michal Koutný <mkoutny@...e.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, JP Kobryn <inwardvessel@...il.com>, 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: [OFFLIST PATCH 2/2] cgroup: use subsystem-specific rstat locks
 to avoid contention

Hi,

On 2025-04-28 23:15:58 -0700, Shakeel Butt wrote:
> Please ignore this patch as it was sent by mistake.

This seems to have made it into next:

748922dcfabd ("cgroup: use subsystem-specific rstat locks to avoid contention")

It causes a BUG and eventually a panic on my Raspberry Pi 1:

WARNING: CPU: 0 PID: 0 at mm/percpu.c:1766 pcpu_alloc_noprof (mm/percpu.c:1766 (discriminator 2)) 
illegal size (0) or align (4) for percpu allocation
CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc7-next-20250521-00086-ga9fb18e56aad #263 NONE
Hardware name: BCM2835
Call trace:
unwind_backtrace from show_stack (arch/arm/kernel/traps.c:259) 
show_stack from dump_stack_lvl (lib/dump_stack.c:122) 
dump_stack_lvl from __warn (kernel/panic.c:729 kernel/panic.c:784) 
__warn from warn_slowpath_fmt (kernel/panic.c:815) 
warn_slowpath_fmt from pcpu_alloc_noprof (mm/percpu.c:1766 (discriminator 2)) 
pcpu_alloc_noprof from ss_rstat_init (kernel/cgroup/rstat.c:515) 
ss_rstat_init from cgroup_init_subsys (kernel/cgroup/cgroup.c:6134 (discriminator 2)) 
cgroup_init_subsys from cgroup_init (kernel/cgroup/cgroup.c:6240) 
cgroup_init from start_kernel (init/main.c:1093) 
 start_kernel from 0x0
...
kernel BUG at kernel/cgroup/cgroup.c:6134!
Internal error: Oops - BUG: 0 [#1] ARM

Reverting resolved it for me.

Regards,
Klara Modin

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