Linux: Add new test misc/tst-sched_setattr-thread

The straightforward sched_getattr call serves as a test for
bug 32781, too.

Reviewed-by: Joseph Myers <josmyers@redhat.com>

sysdeps/unix/sysv/linux/Makefile

@@ -228,6 +228,7 @@ tests += \
   tst-rlimit-infinity \
   tst-sched-affinity-inheritance \
   tst-sched_setattr \
+  tst-sched_setattr-thread \
   tst-scm_rights \
   tst-sigtimedwait \
   tst-sync_file_range \

sysdeps/unix/sysv/linux/tst-sched_setattr-thread.c

@@ -0,0 +1,116 @@
+/* Test for sched_setattr, sched_getattr involving multiple threads.
+   Copyright (C) 2024-2025 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 <sched.h>
+
+#include <stddef.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/xthread.h>
+#include <unistd.h>
+
+enum { initial_nice_value = 15 };
+
+/* Check that thread TID has nice value EXPECTED.  */
+static void
+check_nice_value (int tid, int expected)
+{
+  struct sched_attr attr;
+  if (sched_getattr (tid, &attr, sizeof (attr), 0) != 0)
+    FAIL_EXIT1 ("sched_getattr (%d) failed: %m", tid);
+  TEST_COMPARE (attr.sched_policy, SCHED_OTHER);
+  int nice_value = attr.sched_nice;
+  if (attr.sched_nice != expected)
+    FAIL_EXIT1 ("thread %d: expected nice value %d, got %d"
+                " (called from thread %d)",
+                tid, expected, nice_value,  (int) gettid ());
+  printf ("info: thread %d: nice value %d (called from thread %d)\n",
+          tid, nice_value, (int) gettid ());
+}
+
+/* Set the nice value for TID to VALUE.  */
+static void
+set_nice_value (int tid, int value)
+{
+  struct sched_attr attr =
+    {
+      .size = sizeof (attr),
+      .sched_policy = SCHED_OTHER,
+      .sched_nice = value,
+    };
+  if (sched_setattr (tid, &attr, 0) != 0)
+    FAIL_EXIT1 ("sched_setattr (%d) failed: %m", tid);
+}
+
+static pthread_barrier_t barrier;
+
+static void *
+thread_routine (void *nice_value_ptr)
+{
+  int nice_value = *(int *) nice_value_ptr;
+  /* Check that the nice value was inherited.  */
+  check_nice_value (gettid (), initial_nice_value);
+  xpthread_barrier_wait (&barrier);
+  /* Main thread sets nice value.  */
+  xpthread_barrier_wait (&barrier);
+  check_nice_value (gettid (), nice_value);
+  set_nice_value (gettid (), nice_value + 2);
+  xpthread_barrier_wait (&barrier);
+  /* Main thread sets checks value.  */
+  xpthread_barrier_wait (&barrier);
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  if (nice (initial_nice_value) != initial_nice_value)
+    FAIL_UNSUPPORTED ("cannot set nice value to initial_nice_value: %m");
+
+  xpthread_barrier_init (&barrier, NULL, 3);
+
+  check_nice_value (0, initial_nice_value);
+  check_nice_value (gettid (), initial_nice_value);
+
+  int nice0 = initial_nice_value + 1;
+  pthread_t thr0 = xpthread_create (NULL, thread_routine, &nice0);
+  int nice1 = initial_nice_value + 2;
+  pthread_t thr1 = xpthread_create (NULL, thread_routine, &nice1);
+  check_nice_value (pthread_gettid_np (thr0), initial_nice_value);
+  check_nice_value (pthread_gettid_np (thr1), initial_nice_value);
+  xpthread_barrier_wait (&barrier);
+  set_nice_value (pthread_gettid_np (thr0), nice0);
+  check_nice_value (pthread_gettid_np (thr0), nice0);
+  check_nice_value (pthread_gettid_np (thr1), initial_nice_value);
+  set_nice_value (pthread_gettid_np (thr1), nice1);
+  check_nice_value (pthread_gettid_np (thr0), nice0);
+  check_nice_value (pthread_gettid_np (thr1), nice1);
+  xpthread_barrier_wait (&barrier);
+  /* Threads set nice value.  */
+  xpthread_barrier_wait (&barrier);
+  check_nice_value (pthread_gettid_np (thr0), nice0 + 2);
+  check_nice_value (pthread_gettid_np (thr1), nice1 + 2);
+  xpthread_barrier_wait (&barrier);
+
+  TEST_VERIFY (xpthread_join (thr1) == NULL);
+  TEST_VERIFY (xpthread_join (thr0) == NULL);
+
+  return 0;
+}
+
+#include <support/test-driver.c>