diff options
Diffstat (limited to 'kernel/rcu/tree_stall.h')
| -rw-r--r-- | kernel/rcu/tree_stall.h | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index ffb8cf6c6437..f4152aa18f48 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -718,6 +718,63 @@ static void check_cpu_stall(struct rcu_data *rdp) /* + * Check to see if a failure to end RCU priority inversion was due to + * a CPU not passing through a quiescent state. When this happens, there + * is nothing that RCU priority boosting can do to help, so we shouldn't + * count this as an RCU priority boosting failure. A return of true says + * RCU priority boosting is to blame, and false says otherwise. If false + * is returned, the first of the CPUs to blame is stored through cpup. + * If there was no CPU blocking the current grace period, but also nothing + * in need of being boosted, *cpup is set to -1. This can happen in case + * of vCPU preemption while the last CPU is reporting its quiscent state, + * for example. + * + * If cpup is NULL, then a lockless quick check is carried out, suitable + * for high-rate usage. On the other hand, if cpup is non-NULL, each + * rcu_node structure's ->lock is acquired, ruling out high-rate usage. + */ +bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) +{ + bool atb = false; + int cpu; + unsigned long flags; + struct rcu_node *rnp; + + rcu_for_each_leaf_node(rnp) { + if (!cpup) { + if (READ_ONCE(rnp->qsmask)) { + return false; + } else { + if (READ_ONCE(rnp->gp_tasks)) + atb = true; + continue; + } + } + *cpup = -1; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (rnp->gp_tasks) + atb = true; + if (!rnp->qsmask) { + // No CPUs without quiescent states for this rnp. + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + continue; + } + // Find the first holdout CPU. + for_each_leaf_node_possible_cpu(rnp, cpu) { + if (rnp->qsmask & (1UL << (cpu - rnp->grplo))) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + *cpup = cpu; + return false; + } + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + // Can't blame CPUs, so must blame RCU priority boosting. + return atb; +} +EXPORT_SYMBOL_GPL(rcu_check_boost_fail); + +/* * Show the state of the grace-period kthreads. */ void show_rcu_gp_kthreads(void) |