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rcu: Make rcu_report_unblock_qs_rnp() warn on violated preconditions 

If rcu_report_unblock_qs_rnp() is invoked on something other than
preemptible RCU or if there are still preempted tasks blocking the
current grace period, something went badly wrong in the caller.
This commit therefore adds WARN_ON_ONCE() to these conditions, but
leaving the legitimate reason for early exit (rnp->qsmask != 0)
unwarned.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-04-27 14:05:27 -07:00
parent 8d672fa6bf
commit c74859d1eb
1 changed files with 4 additions and 2 deletions
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6
kernel/rcu/tree.c
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@ -2308,8 +2308,10 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
struct rcu_node *rnp_p;
raw_lockdep_assert_held_rcu_node(rnp);
if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p ||
rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
if (WARN_ON_ONCE(rcu_state_p == &rcu_sched_state) ||
WARN_ON_ONCE(rsp != rcu_state_p) ||
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
rnp->qsmask != 0) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return; /* Still need more quiescent states! */
}