documentation: Catch up list of torture_type options

This commit rids the documentation of long-obsolete torture_type options
such as rcu_sync and adds new ones such as tasks.  Also add verbiage
noting the fact that rcutorture now concurrently tests the asynchrounous,
synchronous, expedited synchronous, and polling grace-period primitives.

Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Miller <davem@davemloft.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Documentation/RCU/torture.txt

@@ -166,40 +166,27 @@ test_no_idle_hz	Whether or not to test the ability of RCU to operate in
 
 torture_type	The type of RCU to test, with string values as follows:
 
-		"rcu":  rcu_read_lock(), rcu_read_unlock() and call_rcu().
-
-		"rcu_sync":  rcu_read_lock(), rcu_read_unlock(), and
-			synchronize_rcu().
-
-		"rcu_expedited": rcu_read_lock(), rcu_read_unlock(), and
-			synchronize_rcu_expedited().
+		"rcu":  rcu_read_lock(), rcu_read_unlock() and call_rcu(),
+			along with expedited, synchronous, and polling
+			variants.
 
 		"rcu_bh": rcu_read_lock_bh(), rcu_read_unlock_bh(), and
-			call_rcu_bh().
-
-		"rcu_bh_sync": rcu_read_lock_bh(), rcu_read_unlock_bh(),
-			and synchronize_rcu_bh().
+			call_rcu_bh(), along with expedited and synchronous
+			variants.
 
-		"rcu_bh_expedited": rcu_read_lock_bh(), rcu_read_unlock_bh(),
-			and synchronize_rcu_bh_expedited().
+		"rcu_busted": This tests an intentionally incorrect version
+			of RCU in order to help test rcutorture itself.
 
 		"srcu": srcu_read_lock(), srcu_read_unlock() and
-			call_srcu().
-
-		"srcu_sync": srcu_read_lock(), srcu_read_unlock() and
-			synchronize_srcu().
-
-		"srcu_expedited": srcu_read_lock(), srcu_read_unlock() and
-			synchronize_srcu_expedited().
+			call_srcu(), along with expedited and
+			synchronous variants.
 
 		"sched": preempt_disable(), preempt_enable(), and
-			call_rcu_sched().
-
-		"sched_sync": preempt_disable(), preempt_enable(), and
-			synchronize_sched().
+			call_rcu_sched(), along with expedited,
+			synchronous, and polling variants.
 
-		"sched_expedited": preempt_disable(), preempt_enable(), and
-			synchronize_sched_expedited().
+		"tasks": voluntary context switch and call_rcu_tasks(),
+			along with expedited and synchronous variants.
 
 		Defaults to "rcu".