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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>
This commit is contained in:
Paul E. McKenney 2011-08-07 20:26:31 -07:00 committed by Paul E. McKenney
parent 82e78d80fc
commit 037067a1b6
1 changed files with 5 additions and 2 deletions
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7
kernel/rcutree.c
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@ -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);