rcu: Rename struct rcu_data .dynticks_snap into .watching_snap

The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, and the snapshot helpers are now prefix by
"rcu_watching". Reflect that change into the storage variables for these
snapshots.

Signed-off-by: Valentin Schneider <[e-mail]>
Reviewed-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Neeraj Upadhyay <[e-mail]>

Documentation/RCU/Design/Data-Structures/Data-Structures.rst

···
 
 ::
 
-     1   int dynticks_snap;
+     1   int watching_snap;
      2   unsigned long dynticks_fqs;
 
-The ``->dynticks_snap`` field is used to take a snapshot of the
+The ``->watching_snap`` field is used to take a snapshot of the
 corresponding CPU's dyntick-idle state when forcing quiescent states,
 and is therefore accessed from other CPUs. Finally, the
 ``->dynticks_fqs`` field is used to count the number of times this CPU

kernel/rcu/tree.c

···
 	 * Ordering between remote CPU's pre idle accesses and post grace period
 	 * updater's accesses is enforced by the below acquire semantic.
 	 */
-	rdp->dynticks_snap = ct_rcu_watching_cpu_acquire(rdp->cpu);
-	if (rcu_watching_snap_in_eqs(rdp->dynticks_snap)) {
+	rdp->watching_snap = ct_rcu_watching_cpu_acquire(rdp->cpu);
+	if (rcu_watching_snap_in_eqs(rdp->watching_snap)) {
 		trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
 		rcu_gpnum_ovf(rdp->mynode, rdp);
 		return 1;
···
 	 * read-side critical section that started before the beginning
 	 * of the current RCU grace period.
 	 */
-	if (rcu_watching_snap_stopped_since(rdp, rdp->dynticks_snap)) {
+	if (rcu_watching_snap_stopped_since(rdp, rdp->watching_snap)) {
 		trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
 		rcu_gpnum_ovf(rnp, rdp);
 		return 1;

kernel/rcu/tree.h

···
 	long		blimit;		/* Upper limit on a processed batch */
 
 	/* 3) dynticks interface. */
-	int dynticks_snap;		/* Per-GP tracking for dynticks. */
+	int  watching_snap;		/* Per-GP tracking for dynticks. */
 	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
 	bool rcu_urgent_qs;		/* GP old need light quiescent state. */
 	bool rcu_forced_tick;		/* Forced tick to provide QS. */