To be sure we have no rcog wake ups that were lost, add a warning to cover the case where the rdp is overloaded with callbacks but no wake up was attempted.
[applied Frederic's adjustment to clearing of nocb_gp_handling flag] Signed-off-by: Joel Fernandes <[email protected]> --- kernel/rcu/tree.c | 4 ++++ kernel/rcu/tree.h | 1 + kernel/rcu/tree_nocb.h | 11 ++++++++++- 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2921ffb19939..958b61be87ea 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3767,6 +3767,10 @@ static void rcu_barrier_entrain(struct rcu_data *rdp) debug_rcu_head_unqueue(&rdp->barrier_head); rcu_barrier_trace(TPS("IRQNQ"), -1, rcu_state.barrier_sequence); } +#ifdef CONFIG_RCU_NOCB_CPU + /* wake_nocb implies all CBs queued before were bypass/lazy. */ + WARN_ON_ONCE(wake_nocb && !rdp->nocb_gp_handling); +#endif rcu_nocb_unlock(rdp); if (wake_nocb) wake_nocb_gp(rdp); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 7dfc57e9adb1..af1d065e3215 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -257,6 +257,7 @@ struct rcu_data { unsigned long nocb_gp_loops; /* # passes through wait code. */ struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ + bool nocb_gp_handling; /* Is rcuog handling this rdp? */ struct task_struct *nocb_cb_kthread; struct list_head nocb_head_rdp; /* * Head of rcu_data list in wakeup chain, diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index f525e4f7985b..acca24670a8c 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -546,6 +546,7 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone, lazy_len = READ_ONCE(rdp->lazy_len); if (was_alldone) { rdp->qlen_last_fqs_check = len; + rdp->nocb_gp_handling = true; rcu_nocb_unlock(rdp); // Only lazy CBs in bypass list if (lazy_len && bypass_len == lazy_len) { @@ -563,7 +564,8 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone, return; } else if (len > rdp->qlen_last_fqs_check + qhimark) { - /* ... or if many callbacks queued. */ + /* Callback overload condition. */ + WARN_ON_ONCE(!rdp->nocb_gp_handling); rdp->qlen_last_fqs_check = len; j = jiffies; if (j != rdp->nocb_gp_adv_time && @@ -732,6 +734,12 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) needwait_gp = true; trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("NeedWaitGP")); + } else if (!rcu_cblist_n_cbs(&rdp->nocb_bypass)) { + /* + * No pending callbacks and no bypass callbacks. + * The rcuog kthread is done handling this rdp. + */ + rdp->nocb_gp_handling = false; } if (rcu_segcblist_ready_cbs(&rdp->cblist)) { needwake = rdp->nocb_cb_sleep; @@ -1254,6 +1262,7 @@ lazy_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) continue; } rcu_nocb_try_flush_bypass(rdp, jiffies); + rdp->nocb_gp_handling = true; rcu_nocb_unlock_irqrestore(rdp, flags); wake_nocb_gp(rdp); sc->nr_to_scan -= _count; -- 2.34.1
