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The rcu_start_this_gp() function had a simple form of funnel locking that used only the leaves and root of the rcu_node tree, which is fine for systems with only a few hundred CPUs, but sub-optimal for systems having thousands of CPUs. This commit therefore adds full-tree funnel locking. This variant of funnel locking is unusual in the following ways: 1. The leaf-level rcu_node structure's ->lock is held throughout. Other funnel-locking implementations drop the leaf-level lock before progressing to the next level of the tree. 2. Funnel locking can be started at the root, which is convenient for code that already holds the root rcu_node structure's ->lock. Other funnel-locking implementations start at the leaves. 3. If an rcu_node structure other than the initial one believes that a grace period is in progress, it is not necessary to go further up the tree. This is because grace-period cleanup scans the full tree, so that marking the need for a subsequent grace period anywhere in the tree suffices -- but only if a grace period is currently in progress. 4. It is possible that the RCU grace-period kthread has not yet started, and this case must be handled appropriately. However, the general approach of using a tree to control lock contention is still in place. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> |
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| .. | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| rcu_segcblist.c | ||
| rcu_segcblist.h | ||
| rcu.h | ||
| rcuperf.c | ||
| rcutorture.c | ||
| srcutiny.c | ||
| srcutree.c | ||
| sync.c | ||
| tiny.c | ||
| tree_exp.h | ||
| tree_plugin.h | ||
| tree.c | ||
| tree.h | ||
| update.c | ||