This is a note to let you know that I've just added the patch titled
rcu/exp: Handle RCU expedited grace period kworker allocation failure
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-exp-handle-rcu-expedited-grace-period-kworker-al.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b10d4abbd4f4eade7cae158972f9125487f07764
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
Date: Fri Jan 12 16:46:16 2024 +0100
rcu/exp: Handle RCU expedited grace period kworker allocation failure
[ Upstream commit e7539ffc9a770f36bacedcf0fbfb4bf2f244f4a5 ]
Just like is done for the kworker performing nodes initialization,
gracefully handle the possible allocation failure of the RCU expedited
grace period main kworker.
While at it perform a rename of the related checking functions to better
reflect the expedited specifics.
Reviewed-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker")
Signed-off-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>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2e8d4572e8620..8cf6a6fef7965 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4671,6 +4671,7 @@ static void __init rcu_start_exp_gp_kworkers(void)
rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name);
if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) {
pr_err("Failed to create %s!\n", gp_kworker_name);
+ rcu_exp_gp_kworker = NULL;
return;
}
@@ -4679,6 +4680,7 @@ static void __init rcu_start_exp_gp_kworkers(void)
pr_err("Failed to create %s!\n", par_gp_kworker_name);
rcu_exp_par_gp_kworker = NULL;
kthread_destroy_worker(rcu_exp_gp_kworker);
+ rcu_exp_gp_kworker = NULL;
return;
}
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 6e87dc764f471..733b18077f5a0 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -428,7 +428,12 @@ static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp)
__sync_rcu_exp_select_node_cpus(rewp);
}
-static inline bool rcu_gp_par_worker_started(void)
+static inline bool rcu_exp_worker_started(void)
+{
+ return !!READ_ONCE(rcu_exp_gp_kworker);
+}
+
+static inline bool rcu_exp_par_worker_started(void)
{
return !!READ_ONCE(rcu_exp_par_gp_kworker);
}
@@ -478,7 +483,12 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
__sync_rcu_exp_select_node_cpus(rewp);
}
-static inline bool rcu_gp_par_worker_started(void)
+static inline bool rcu_exp_worker_started(void)
+{
+ return !!READ_ONCE(rcu_gp_wq);
+}
+
+static inline bool rcu_exp_par_worker_started(void)
{
return !!READ_ONCE(rcu_par_gp_wq);
}
@@ -541,7 +551,7 @@ static void sync_rcu_exp_select_cpus(void)
rnp->exp_need_flush = false;
if (!READ_ONCE(rnp->expmask))
continue; /* Avoid early boot non-existent wq. */
- if (!rcu_gp_par_worker_started() ||
+ if (!rcu_exp_par_worker_started() ||
rcu_scheduler_active != RCU_SCHEDULER_RUNNING ||
rcu_is_last_leaf_node(rnp)) {
/* No worker started yet or last leaf, do direct call. */
@@ -952,7 +962,7 @@ static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp)
*/
void synchronize_rcu_expedited(void)
{
- bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT);
+ bool use_worker;
unsigned long flags;
struct rcu_exp_work rew;
struct rcu_node *rnp;
@@ -963,6 +973,9 @@ void synchronize_rcu_expedited(void)
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu_expedited() in RCU read-side critical section");
+ use_worker = (rcu_scheduler_active != RCU_SCHEDULER_INIT) &&
+ rcu_exp_worker_started();
+
/* Is the state is such that the call is a grace period? */
if (rcu_blocking_is_gp()) {
// Note well that this code runs with !PREEMPT && !SMP.
@@ -992,7 +1005,7 @@ void synchronize_rcu_expedited(void)
return; /* Someone else did our work for us. */
/* Ensure that load happens before action based on it. */
- if (unlikely(boottime)) {
+ if (unlikely(!use_worker)) {
/* Direct call during scheduler init and early_initcalls(). */
rcu_exp_sel_wait_wake(s);
} else {
@@ -1010,7 +1023,7 @@ void synchronize_rcu_expedited(void)
/* Let the next expedited grace period start. */
mutex_unlock(&rcu_state.exp_mutex);
- if (likely(!boottime))
+ if (likely(use_worker))
synchronize_rcu_expedited_destroy_work(&rew);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
