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().
Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions")
Link: https://lore.kernel.org/r/20240528121928.i-Gu7Jvg@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
On 2024-05-28 15:44:51 [+0200], Vlastimil Babka (SUSE) wrote:
> I think just s/memcg_stats_lock()/__mod_memcg_lruvec_state()/ in your
> phrasing, since we are removing the lockdep assert from path that calls
> __mod_memcg_lruvec_state() and not memcg_stats_lock()?
> Or am I missing something?
Yeah, makes sense.
mm/memcontrol.c | 2 --
1 file changed, 2 deletions(-)
--- a/mm/memcontrol.c
+++ b/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);
