From: Frederic Weisbecker frederic@kernel.org
[ 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@google.com Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker") Signed-off-by: Frederic Weisbecker frederic@kernel.org Reviewed-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/rcu/tree.c | 2 ++ kernel/rcu/tree_exp.h | 25 +++++++++++++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-)
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);