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rcu/nocb: Make rcutree_migrate_callbacks() start at leaf rcu_node structure
Because rcutree_migrate_callbacks() is invoked infrequently and because an exact snapshot of the grace-period state might save some callbacks a second trip through a grace period, this function has used the root rcu_node structure. However, this safe-second-trip optimization happens only if rcutree_migrate_callbacks() races with grace-period initialization, so it is not worth the added mental load. This commit therefore makes rcutree_migrate_callbacks() start with the leaf rcu_node structures, as is done elsewhere. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
parent
750d7f6a43
commit
c00045be32
1 changed files with 6 additions and 5 deletions
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@ -3157,8 +3157,8 @@ void rcutree_migrate_callbacks(int cpu)
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{
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unsigned long flags;
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struct rcu_data *my_rdp;
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struct rcu_node *my_rnp;
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struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
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struct rcu_node *rnp_root = rcu_get_root();
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bool needwake;
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if (rcu_segcblist_is_offloaded(&rdp->cblist) ||
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@ -3167,18 +3167,19 @@ void rcutree_migrate_callbacks(int cpu)
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local_irq_save(flags);
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my_rdp = this_cpu_ptr(&rcu_data);
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my_rnp = my_rdp->mynode;
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if (rcu_nocb_adopt_orphan_cbs(my_rdp, rdp, flags)) {
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local_irq_restore(flags);
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return;
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}
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raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
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raw_spin_lock_rcu_node(my_rnp); /* irqs already disabled. */
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/* Leverage recent GPs and set GP for new callbacks. */
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needwake = rcu_advance_cbs(rnp_root, rdp) ||
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rcu_advance_cbs(rnp_root, my_rdp);
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needwake = rcu_advance_cbs(my_rnp, rdp) ||
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rcu_advance_cbs(my_rnp, my_rdp);
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rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist);
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WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) !=
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!rcu_segcblist_n_cbs(&my_rdp->cblist));
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raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags);
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raw_spin_unlock_irqrestore_rcu_node(my_rnp, flags);
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if (needwake)
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rcu_gp_kthread_wake();
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WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||
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