[PATCH 38/48] rcu: Allocate WQ with WQ_MEM_RECLAIM bit set

Uladzislau Rezki (Sony)
2024-05-07T09:36:12Z

synchronize_rcu() users have to be processed regardless
of memory pressure so our private WQ needs to have at least
one execution context what WQ_MEM_RECLAIM flag guarantees.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
kernel/rcu/tree.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a270abade4d..1d5c000e5c7a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1582,6 +1582,7 @@ static void rcu_sr_put_wait_head(struct llist_node *node)
/* Disabled by default. */
static int rcu_normal_wake_from_gp;
module_param(rcu_normal_wake_from_gp, int, 0644);
+static struct workqueue_struct *sync_wq;

static void rcu_sr_normal_complete(struct llist_node *node)
{
@@ -1680,7 +1681,7 @@ static void rcu_sr_normal_gp_cleanup(void)
* of outstanding users(if still left) and releasing wait-heads
* added by rcu_sr_normal_gp_init() call.
*/
- schedule_work(&rcu_state.srs_cleanup_work);
+ queue_work(sync_wq, &rcu_state.srs_cleanup_work);
}

/*
@@ -5585,6 +5586,9 @@ void __init rcu_init(void)
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_gp_wq);

+ sync_wq = alloc_workqueue("sync_wq", WQ_MEM_RECLAIM, 0);
+ WARN_ON(!sync_wq);
+
/* Fill in default value for rcutree.qovld boot parameter. */
/* -After- the rcu_node ->lock fields are initialized! */
if (qovld < 0)
--
2.39.2