Commit 037067a1 authored Aug 07, 2011 by Paul E. McKenney Committed by Paul E. McKenney Sep 28, 2011

rcu: Prohibit grace periods during early boot

Greater use of RCU during early boot (before the scheduler is operating)
is causing RCU to attempt to start grace periods during that time, which
in turn is resulting in both RCU and the callback functions attempting
to use the scheduler before it is ready.

This commit prevents these problems by prohibiting RCU grace periods
until after the scheduler has spawned the first non-idle task.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent 82e78d80

kernel/rcutree.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -838,8 +838,11 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
		struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
		struct rcu_node *rnp = rcu_get_root(rsp);

		if (!cpu_needs_another_gp(rsp, rdp) \|\| rsp->fqs_active) {
		if (cpu_needs_another_gp(rsp, rdp))
		if (!rcu_scheduler_fully_active \|\|
		!cpu_needs_another_gp(rsp, rdp) \|\|
		rsp->fqs_active) {
		if (rcu_scheduler_fully_active &&
		cpu_needs_another_gp(rsp, rdp))
		rsp->fqs_need_gp = 1;
		if (rnp->completed == rsp->completed) {
		raw_spin_unlock_irqrestore(&rnp->lock, flags);

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