svn commit: r357894 - head/lib/libthr/thread

[Konstantin Belousov]

Author: kib
Date: Thu Feb 13 23:22:12 2020
New Revision: 357894
URL: https://svnweb.freebsd.org/changeset/base/357894

Log:
  Return success, instead of ESRCH, from pthread_cancel(3) applied to the
  exited but not yet joined thread.
  
  Before, if the thread exited but was not yet joined, we returned
  ESRCH.
  
  According to IEEE Std 1003.1™-2017 recommendation in the
  description of pthread_cancel(3):
    If an implementation detects use of a thread ID after the end of its
    lifetime, it is recommended that the function should fail and report
    an [ESRCH] error.
  So it seems desirable to not return ESRCH until the lifetime of the
  thread ID ends.  According to the section 2.9.2 Thread IDs,
    The lifetime of a thread ID ends after the thread terminates if it
    was created with the detachstate attribute set to
    PTHREAD_CREATE_DETACHED or if pthread_detach() or pthread_join()
    has been called for that thread.
  In other words, lifetime for thread ID of exited but not yet joined thread
  did not ended yet.
  
  Prompted by:	cperciva
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/lib/libthr/thread/thr_cancel.c

Modified: head/lib/libthr/thread/thr_cancel.c
==============================================================================
--- head/lib/libthr/thread/thr_cancel.c	Thu Feb 13 23:18:35 2020	(r357893)
+++ head/lib/libthr/thread/thr_cancel.c	Thu Feb 13 23:22:12 2020	(r357894)
@@ -71,7 +71,7 @@ _thr_cancel(pthread_t pthread)
 	 * _thr_find_thread and THR_THREAD_UNLOCK will enter and leave critical
 	 * region automatically.
 	 */
-	if ((ret = _thr_find_thread(curthread, pthread, 0)) == 0) {
+	if ((ret = _thr_find_thread(curthread, pthread, 1)) == 0) {
 		if (!pthread->cancel_pending) {
 			pthread->cancel_pending = 1;
 			if (pthread->state != PS_DEAD)