Backport: Improve sem_trywait test coverage

Resolves: RHEL-65354

glibc-RHEL-65354.patch

@@ -0,0 +1,109 @@
+commit 3c2b9dc41cd05da055fae6f793a355063156bdf3
+Author: Joseph Myers <josmyers@redhat.com>
+Date:   Fri Nov 29 20:25:04 2024 +0000
+
+    Add threaded test of sem_trywait
+    
+    All the existing glibc tests of sem_trywait are single-threaded.  Add
+    one that calls sem_trywait and sem_post in separate threads.
+    
+    Tested for x86_64.
+
+Conflicts:
+	sysdeps/pthread/Makefile (add new test)
+
+diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile
+index 6355e94171fbcdc3..5a1b26fa3c0e6061 100644
+--- a/sysdeps/pthread/Makefile
++++ b/sysdeps/pthread/Makefile
+@@ -128,6 +128,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
+ 	 tst-pthread_kill-exiting \
+ 	 tst-cancel30 \
+   tst-spin5 \
++  tst-sem19 \
+ 	 # tests
+ 
+ tests-time64 := \
+diff --git a/sysdeps/pthread/tst-sem19.c b/sysdeps/pthread/tst-sem19.c
+new file mode 100644
+index 0000000000000000..9ef461e008ab9eab
+--- /dev/null
++++ b/sysdeps/pthread/tst-sem19.c
+@@ -0,0 +1,77 @@
++/* Test sem_trywait with threads.
++   Copyright (C) 2024 Free Software Foundation, Inc.
++   This file is part of the GNU C Library.
++
++   The GNU C Library is free software; you can redistribute it and/or
++   modify it under the terms of the GNU Lesser General Public
++   License as published by the Free Software Foundation; either
++   version 2.1 of the License, or (at your option) any later version.
++
++   The GNU C Library is distributed in the hope that it will be useful,
++   but WITHOUT ANY WARRANTY; without even the implied warranty of
++   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
++   Lesser General Public License for more details.
++
++   You should have received a copy of the GNU Lesser General Public
++   License along with the GNU C Library; if not, see
++   <https://www.gnu.org/licenses/>.  */
++
++#include <errno.h>
++#include <pthread.h>
++#include <semaphore.h>
++#include <support/check.h>
++#include <support/xthread.h>
++
++/* The test uses two threads, the main thread and a newly created
++   thread to test the operation of sem_trywait in a threaded scenario.
++   The intent is to test sem_trywait when it would return EAGAIN, and
++   then again after the critical section in the new thread has posted
++   to the semaphore and the main thread succeeds in calling
++   sem_trywait.  It is possible this test fails with a timeout if the
++   second thread takes longer than the test timeout to acquire the
++   lock, and post.  */
++
++static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
++static sem_t sem;
++
++static void *
++tf (void *arg)
++{
++  xpthread_mutex_lock (&lock);
++  sem_post (&sem);
++  xpthread_mutex_unlock (&lock);
++  return NULL;
++}
++
++static int
++do_test (void)
++{
++  int ret;
++
++  ret = sem_init (&sem, 0, 0);
++  TEST_VERIFY_EXIT (ret == 0);
++  xpthread_mutex_lock (&lock);
++  pthread_t th = xpthread_create (NULL, tf, NULL);
++  errno = 0;
++  /* The other thread is waiting on the lock before it calls sem_post,
++     so sem_trywait should fail.  */
++  ret = sem_trywait (&sem);
++  TEST_COMPARE (ret, -1);
++  TEST_COMPARE (errno, EAGAIN);
++  xpthread_mutex_unlock (&lock);
++  /* The other thread now takes the lock, calls sem_post and releases
++     the lock.  */
++  for (;;)
++    {
++      errno = 0;
++      ret = sem_trywait (&sem);
++      if (ret == 0)
++	break;
++      TEST_COMPARE (errno, EAGAIN);
++    }
++  xpthread_join (th);
++
++  return 0;
++}
++
++#include <support/test-driver.c>

glibc.spec

@@ -1052,6 +1052,7 @@ Patch744: glibc-RHEL-68850-1.patch
 Patch745: glibc-RHEL-68850-2.patch
 Patch746: glibc-RHEL-61568.patch
 Patch747: glibc-RHEL-58979.patch
+Patch748: glibc-RHEL-65354.patch
 
 ##############################################################################
 # Continued list of core "glibc" package information:
@@ -3065,6 +3066,7 @@ update_gconv_modules_cache ()
 - Backport: Improve pthread_spin_trylock test coverage (RHEL-61568)
 - Backport: Implement test to verify dynamic linker behaves correctly in case
   of hash collision for the symbol name and symbol version. (RHEL-58979)
+- Backport: Improve sem_trywait test coverage (RHEL-65354)
 
 * Thu Dec 19 2024 DJ Delorie <dj@redhat.com> - 2.34-148
 - Increase ungetc test coverage, guarantee single char pushback (RHEL-46738)