The patch titled
Subject: memcg: remove the lockdep assert from __mod_objcg_mlstate()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
memcg-remove-the-lockdep-assert-from-__mod_objcg_mlstate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-remove-the-lockdep-assert-from-__mod_objcg_mlstate.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: memcg: remove the lockdep assert from __mod_objcg_mlstate()
Date: Tue, 28 May 2024 16:13:41 +0200
The assert was introduced in the commit cited below as an insurance that
the semantic is the same after the local_irq_save() has been removed and
the function has been made static.
The original requirement to disable interrupt was due the modification
of per-CPU counters which require interrupts to be disabled because the
counter update operation is not atomic and some of the counters are
updated from interrupt context.
All callers of __mod_objcg_mlstate() acquire a lock
(memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and
the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not
disabled and the assert triggers.
The safety of the counter update is already ensured by
VM_WARN_ON_IRQS_ENABLED() which is part of __mod_memcg_lruvec_state() and
does not require yet another check.
Remove the lockdep assert from __mod_objcg_mlstate().
Link: https://lkml.kernel.org/r/20240528141341.rz_rytN_@xxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20240528121928.i-Gu7Jvg@xxxxxxxxxxxxx
Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 2 --
1 file changed, 2 deletions(-)
--- a/mm/memcontrol.c~memcg-remove-the-lockdep-assert-from-__mod_objcg_mlstate
+++ a/mm/memcontrol.c
@@ -3147,8 +3147,6 @@ static inline void __mod_objcg_mlstate(s
struct mem_cgroup *memcg;
struct lruvec *lruvec;
- lockdep_assert_irqs_disabled();
-
rcu_read_lock();
memcg = obj_cgroup_memcg(objcg);
lruvec = mem_cgroup_lruvec(memcg, pgdat);
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
memcg-remove-the-lockdep-assert-from-__mod_objcg_mlstate.patch
