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Offloading and de-offloading RCU callback processes must be done carefully. There must never be a time at which callback processing is disabled because the task driving the offloading or de-offloading might be preempted or otherwise stalled at that point in time, which would result in OOM due to calbacks piling up indefinitely. This implies that there will be times during which a given CPU's callbacks might be concurrently invoked by both that CPU's RCU_SOFTIRQ handler (or, equivalently, that CPU's rcuc kthread) and by that CPU's rcuo kthread. This situation could fatally confuse both rcu_barrier() and the CPU-hotplug offlining process, so these must be excluded during any concurrent-callback-invocation period. In addition, during times of concurrent callback invocation, changes to ->cblist must be protected both as needed for RCU_SOFTIRQ and as needed for the rcuo kthread. This commit therefore defines and documents the states for a state machine that coordinates offloading and deoffloading. Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Cc: Thomas Gleixner <tglx@linutronix.de> Inspired-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> |
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| .. | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| rcu.h | ||
| rcu_segcblist.c | ||
| rcu_segcblist.h | ||
| rcuscale.c | ||
| rcutorture.c | ||
| refscale.c | ||
| srcutiny.c | ||
| srcutree.c | ||
| sync.c | ||
| tasks.h | ||
| tiny.c | ||
| tree.c | ||
| tree.h | ||
| tree_exp.h | ||
| tree_plugin.h | ||
| tree_stall.h | ||
| update.c | ||