rcu-tasks: Fix synchronize_rcu_tasks_trace() header comment

The synchronize_rcu_tasks_trace() header comment incorrectly claims that
any number of things delimit RCU Tasks Trace read-side critical sections,
when in fact only rcu_read_lock_trace() and rcu_read_unlock_trace() do so.
This commit therefore fixes this comment, and, while in the area, fixes
a typo in the rcu_read_lock_trace() header comment.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

include/linux/rcupdate_trace.h

@@ -36,8 +36,8 @@ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting);
 /**
  * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section
  *
- * When synchronize_rcu_trace() is invoked by one task, then that task
- * is guaranteed to block until all other tasks exit their read-side
+ * When synchronize_rcu_tasks_trace() is invoked by one task, then that
+ * task is guaranteed to block until all other tasks exit their read-side
  * critical sections.  Similarly, if call_rcu_trace() is invoked on one
  * task while other tasks are within RCU read-side critical sections,
  * invocation of the corresponding RCU callback is deferred until after

kernel/rcu/tasks.h

@@ -1118,11 +1118,10 @@ EXPORT_SYMBOL_GPL(call_rcu_tasks_trace);
  * synchronize_rcu_tasks_trace - wait for a trace rcu-tasks grace period
  *
  * Control will return to the caller some time after a trace rcu-tasks
- * grace period has elapsed, in other words after all currently
- * executing rcu-tasks read-side critical sections have elapsed.  These
- * read-side critical sections are delimited by calls to schedule(),
- * cond_resched_tasks_rcu_qs(), userspace execution, and (in theory,
- * anyway) cond_resched().
+ * grace period has elapsed, in other words after all currently executing
+ * rcu-tasks read-side critical sections have elapsed.  These read-side
+ * critical sections are delimited by calls to rcu_read_lock_trace()
+ * and rcu_read_unlock_trace().
  *
  * This is a very specialized primitive, intended only for a few uses in
  * tracing and other situations requiring manipulation of function preambles