6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zqiang <qiang.zhang1211@xxxxxxxxx>
[ Upstream commit dda98810b552fc6bf650f4270edeebdc2f28bd3f ]
For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and
CONFIG_RCU_LAZY=y, the following scenarios will trigger WARN_ON_ONCE()
in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions:
CPU2 CPU11
kthread
rcu_nocb_cb_kthread ksys_write
rcu_do_batch vfs_write
rcu_torture_timer_cb proc_sys_write
__kmem_cache_free proc_sys_call_handler
kmemleak_free drop_caches_sysctl_handler
delete_object_full drop_slab
__delete_object shrink_slab
put_object lazy_rcu_shrink_scan
call_rcu rcu_nocb_flush_bypass
__call_rcu_commn rcu_nocb_bypass_lock
raw_spin_trylock(&rdp->nocb_bypass_lock) fail
atomic_inc(&rdp->nocb_lock_contended);
rcu_nocb_wait_contended WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) |
|_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ _ _ _ _ _ _ _ _ __|
Reproduce this bug with "echo 3 > /proc/sys/vm/drop_caches".
This commit therefore uses rcu_nocb_try_flush_bypass() instead of
rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(). If the nocb_bypass
queue is being flushed, then rcu_nocb_try_flush_bypass will return
directly.
Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/rcu/tree_nocb.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 5598212d1f274..2b24405b9cd2b 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1383,7 +1383,7 @@ lazy_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
rcu_nocb_unlock_irqrestore(rdp, flags);
continue;
}
- WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies, false));
+ rcu_nocb_try_flush_bypass(rdp, jiffies);
rcu_nocb_unlock_irqrestore(rdp, flags);
wake_nocb_gp(rdp, false);
sc->nr_to_scan -= _count;
--
2.43.0
