srcu: Make rcutorture writer stalls print SRCU GP state

In the past, SRCU was simple enough that there was little point in
making the rcutorture writer stall messages print the SRCU grace-period
number state.  With the advent of Tree SRCU, this has changed.  This
commit therefore makes Classic, Tiny, and Tree SRCU report this state
to rcutorture as needed.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Mike Galbraith <efault@gmx.de>

include/linux/srcuclassic.h

@@ -98,4 +98,18 @@ void synchronize_srcu_expedited(struct srcu_struct *sp);
 void srcu_barrier(struct srcu_struct *sp);
 unsigned long srcu_batches_completed(struct srcu_struct *sp);
 
+static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
+					   struct srcu_struct *sp, int *flags,
+					   unsigned long *gpnum,
+					   unsigned long *completed)
+{
+	if (test_type != SRCU_FLAVOR)
+		return;
+	*flags = 0;
+	*completed = sp->completed;
+	*gpnum = *completed;
+	if (sp->batch_queue.head || sp->batch_check0.head || sp->batch_check0.head)
+		(*gpnum)++;
+}
+
 #endif

include/linux/srcutiny.h

@@ -78,4 +78,16 @@ static inline unsigned long srcu_batches_completed(struct srcu_struct *sp)
 	return 0;
 }
 
+static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
+					   struct srcu_struct *sp, int *flags,
+					   unsigned long *gpnum,
+					   unsigned long *completed)
+{
+	if (test_type != SRCU_FLAVOR)
+		return;
+	*flags = 0;
+	*completed = sp->srcu_gp_seq;
+	*gpnum = *completed;
+}
+
 #endif

include/linux/srcutree.h

@@ -140,4 +140,8 @@ void synchronize_srcu_expedited(struct srcu_struct *sp);
 void srcu_barrier(struct srcu_struct *sp);
 unsigned long srcu_batches_completed(struct srcu_struct *sp);
 
+void srcutorture_get_gp_data(enum rcutorture_type test_type,
+			     struct srcu_struct *sp, int *flags,
+			     unsigned long *gpnum, unsigned long *completed);
+
 #endif

kernel/rcu/rcutorture.c

@@ -1360,12 +1360,14 @@ rcu_torture_stats_print(void)
 		cur_ops->stats();
 	if (rtcv_snap == rcu_torture_current_version &&
 	    rcu_torture_current != NULL) {
-		int __maybe_unused flags;
-		unsigned long __maybe_unused gpnum;
-		unsigned long __maybe_unused completed;
+		int __maybe_unused flags = 0;
+		unsigned long __maybe_unused gpnum = 0;
+		unsigned long __maybe_unused completed = 0;
 
 		rcutorture_get_gp_data(cur_ops->ttype,
 				       &flags, &gpnum, &completed);
+		srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
+					&flags, &gpnum, &completed);
 		wtp = READ_ONCE(writer_task);
 		pr_alert("??? Writer stall state %s(%d) g%lu c%lu f%#x ->state %#lx\n",
 			 rcu_torture_writer_state_getname(),

kernel/rcu/srcutree.c

@@ -1011,3 +1011,16 @@ void process_srcu(struct work_struct *work)
 	srcu_reschedule(sp, atomic_read(&sp->srcu_exp_cnt) ? 0 : SRCU_INTERVAL);
 }
 EXPORT_SYMBOL_GPL(process_srcu);
+
+void srcutorture_get_gp_data(enum rcutorture_type test_type,
+					   struct srcu_struct *sp, int *flags,
+					   unsigned long *gpnum,
+					   unsigned long *completed)
+{
+	if (test_type != SRCU_FLAVOR)
+		return;
+	*flags = 0;
+	*completed = rcu_seq_ctr(sp->srcu_gp_seq);
+	*gpnum = rcu_seq_ctr(sp->srcu_gp_seq_needed);
+}
+EXPORT_SYMBOL_GPL(srcutorture_get_gp_data);

kernel/rcu/tree.c

@@ -704,15 +704,11 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 	default:
 		break;
 	}
-	if (rsp != NULL) {
-		*flags = READ_ONCE(rsp->gp_flags);
-		*gpnum = READ_ONCE(rsp->gpnum);
-		*completed = READ_ONCE(rsp->completed);
+	if (rsp == NULL)
 		return;
-	}
-	*flags = 0;
-	*gpnum = 0;
-	*completed = 0;
+	*flags = READ_ONCE(rsp->gp_flags);
+	*gpnum = READ_ONCE(rsp->gpnum);
+	*completed = READ_ONCE(rsp->completed);
 }
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);