rcu: Add debug checks to TREE_PREEMPT_RCU for premature grace periods

Check to make sure that there are no blocked tasks for the previous
grace period while initializing for the next grace period, verify
that rcu_preempt_qs() is given the correct CPU number and is never
called for an offline CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12528585111986-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index da301e2fd84f..e9a4ae94647f 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -632,6 +632,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         /* Special-case the common single-level case. */
         if (NUM_RCU_NODES == 1) {
                 rnp->qsmask = rnp->qsmaskinit;
+                rcu_preempt_check_blocked_tasks(rnp);
                 rnp->gpnum = rsp->gpnum;
                 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
                 spin_unlock_irqrestore(&rnp->lock, flags);
@@ -665,6 +666,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++) {
                 spin_lock(&rnp_cur->lock);      /* irqs already disabled. */
                 rnp_cur->qsmask = rnp_cur->qsmaskinit;
+                rcu_preempt_check_blocked_tasks(rnp);
                 rnp->gpnum = rsp->gpnum;
                 spin_unlock(&rnp_cur->lock);    /* irqs already disabled. */
         }