rcu: Make quiescent-state reporting use ->gp_seq

This commit switches the functions reporting quiescent states from
use of ->gpnum to ->gp_seq.  In either case, the point is to handle
races where a given grace period ends before a quiescent state can
be reported.  Failing to catch these races would result in too-short
grace periods, hence the checking.

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

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 002f853..a54587d 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2242,7 +2242,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
  * must be represented by the same rcu_node structure (which need not be a
  * leaf rcu_node structure, though it often will be).  The gps parameter
  * is the grace-period snapshot, which means that the quiescent states
  * must be represented by the same rcu_node structure (which need not be a
  * leaf rcu_node structure, though it often will be).  The gps parameter
  * is the grace-period snapshot, which means that the quiescent states

- * are valid only if rnp->gpnum is equal to gps.  That structure's lock
+ * are valid only if rnp->gp_seq is equal to gps.  That structure's lock

  * must be held upon entry, and it is released before return.
  */
 static void
  * must be held upon entry, and it is released before return.
  */
 static void


@@ -2257,7 +2257,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
 
        /* Walk up the rcu_node hierarchy. */
        for (;;) {
 
        /* Walk up the rcu_node hierarchy. */
        for (;;) {

-               if (!(rnp->qsmask & mask) || rnp->gpnum != gps) {
+               if (!(rnp->qsmask & mask) || rnp->gp_seq != gps) {

 
                        /*
                         * Our bit has already been cleared, or the
 
                        /*
                         * Our bit has already been cleared, or the


@@ -2335,8 +2335,8 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
                return;
        }
 
                return;
        }
 

-       /* Report up the rest of the hierarchy, tracking current ->gpnum. */
-       gps = rnp->gpnum;
+       /* Report up the rest of the hierarchy, tracking current ->gp_seq. */
+       gps = rnp->gp_seq;

        mask = rnp->grpmask;
        raw_spin_unlock_rcu_node(rnp);  /* irqs remain disabled. */
        raw_spin_lock_rcu_node(rnp_p);  /* irqs already disabled. */
        mask = rnp->grpmask;
        raw_spin_unlock_rcu_node(rnp);  /* irqs remain disabled. */
        raw_spin_lock_rcu_node(rnp_p);  /* irqs already disabled. */


@@ -2357,8 +2357,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 
        rnp = rdp->mynode;
        raw_spin_lock_irqsave_rcu_node(rnp, flags);
 
        rnp = rdp->mynode;
        raw_spin_lock_irqsave_rcu_node(rnp, flags);

-       if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum ||
-           rnp->completed == rnp->gpnum || rdp->gpwrap) {
+       if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
+           rdp->gpwrap) {

 
                /*
                 * The grace period in which this quiescent state was
 
                /*
                 * The grace period in which this quiescent state was


@@ -2383,7 +2383,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
                 */
                needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
 
                 */
                needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
 

-               rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
+               rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);

                /* ^^^ Released rnp->lock */
                if (needwake)
                        rcu_gp_kthread_wake(rsp);
                /* ^^^ Released rnp->lock */
                if (needwake)
                        rcu_gp_kthread_wake(rsp);


@@ -2688,8 +2688,8 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp))
                        }
                }
                if (mask != 0) {
                        }
                }
                if (mask != 0) {

-                       /* Idle/offline CPUs, report (releases rnp->lock. */
-                       rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
+                       /* Idle/offline CPUs, report (releases rnp->lock). */
+                       rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);

                } else {
                        /* Nothing to do here, so just drop the lock. */
                        raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
                } else {
                        /* Nothing to do here, so just drop the lock. */
                        raw_spin_unlock_irqrestore_rcu_node(rnp, flags);