openmp: Fix intermittent hanging of task-detach-6 libgomp tests [PR98738]

openmp: Fix intermittent hanging of task-detach-6 libgomp tests [PR98738]

This adds support for the task detach clause to taskwait, and fixes a
number of problems related to semaphores that may lead to a hang in
some circumstances.

2021-01-21  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgomp/

	PR libgomp/98738
	* libgomp.h (enum gomp_task_kind): Add GOMP_TASK_DETACHED.
	* task.c (task_fulfilled_p): Check detach field as well.
	(GOMP_task): Add thread to debug messages.  Use address of task as
	the event handle.
	(gomp_barrier_handle_tasks): Fix indentation.  Use address of task
	as event handle. Set kind of suspended detach task to
	GOMP_TASK_DETACHED and decrement task_running_count.  Move
	finish_cancelled block out of else branch.  Skip decrement of
	task_running_count if task kind is GOMP_TASK_DETACHED.
	(GOMP_taskwait): Finish fulfilled detach tasks.  Update comment.
	Queue detach tasks that have not been fulfilled.
	(omp_fulfill_event): Use address of task as event handle.  Post
	to taskwait_sem and taskgroup_sem if necessary.  Check
	task_running_count before calling gomp_team_barrier_wake.
	* testsuite/libgomp.c-c++-common/task-detach-5.c (main): Change
	data-sharing of detach events on enclosing parallel to private.
	* testsuite/libgomp.c-c++-common/task-detach-6.c (main): Likewise.
	* testsuite/libgomp.fortran/task-detach-5.f90 (task_detach_5):
	Likewise.
	* testsuite/libgomp.fortran/task-detach-6.f90 (task_detach_6):
	Likewise.