rcu: Eliminate synchronize_rcu_mult()

Now that synchronize_rcu() waits for both RCU read-side critical
sections and preempt-disabled regions of code, the sole caller of
synchronize_rcu_mult() can be replaced by synchronize_rcu().
This patch makes this change and removes synchronize_rcu_mult().
Note that _wait_rcu_gp() still supports synchronize_rcu_mult(),
and thus might be simplified in the future to take only take
a single call_rcu() function rather than the current list of them.

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

include/linux/rcupdate_wait.h

@@ -31,21 +31,4 @@ do {									\
 
 #define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__)
 
-/**
- * synchronize_rcu_mult - Wait concurrently for multiple grace periods
- * @...: List of call_rcu() functions for different grace periods to wait on
- *
- * This macro waits concurrently for multiple types of RCU grace periods.
- * For example, synchronize_rcu_mult(call_rcu, call_rcu_tasks) would wait
- * on concurrent RCU and RCU-tasks grace periods.  Waiting on a give SRCU
- * domain requires you to write a wrapper function for that SRCU domain's
- * call_srcu() function, supplying the corresponding srcu_struct.
- *
- * If Tiny RCU, tell _wait_rcu_gp() does not bother waiting for RCU,
- * given that anywhere synchronize_rcu_mult() can be called is automatically
- * a grace period.
- */
-#define synchronize_rcu_mult(...) \
-	_wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)
-
 #endif /* _LINUX_SCHED_RCUPDATE_WAIT_H */

kernel/rcu/update.c

@@ -335,8 +335,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 	/* Initialize and register callbacks for each crcu_array element. */
 	for (i = 0; i < n; i++) {
 		if (checktiny &&
-		    (crcu_array[i] == call_rcu ||
-		     crcu_array[i] == call_rcu_bh)) {
+		    (crcu_array[i] == call_rcu)) {
 			might_sleep();
 			continue;
 		}
@@ -352,8 +351,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 	/* Wait for all callbacks to be invoked. */
 	for (i = 0; i < n; i++) {
 		if (checktiny &&
-		    (crcu_array[i] == call_rcu ||
-		     crcu_array[i] == call_rcu_bh))
+		    (crcu_array[i] == call_rcu))
 			continue;
 		for (j = 0; j < i; j++)
 			if (crcu_array[j] == crcu_array[i])

kernel/sched/core.c

@@ -5788,7 +5788,7 @@ int sched_cpu_deactivate(unsigned int cpu)
 	 *
 	 * Do sync before park smpboot threads to take care the rcu boost case.
 	 */
-	synchronize_rcu_mult(call_rcu, call_rcu_sched);
+	synchronize_rcu();
 
 	if (!sched_smp_initialized)
 		return 0;