Remove CPU set size checking from affinity functions [BZ #19143]

With current kernel versions, the check does not reliably detect that
unavailable CPUs are requested, for these reasons:

(1) The kernel will silently ignore non-allowed CPUs, that is, CPUs
    which are physically present but disallowed for the thread
    based on system configuration.

(2) Similarly, CPU bits which lack an online CPU (possible CPUs)
    are ignored.

(3) The existing probing code assumes that the CPU mask size is a
    power of two and at least 1024.  Neither has it to be a power
    of two, nor is the minimum possible value 1024, so the value
    determined is often too large.  This means that the CPU set
    size check in glibc accepts CPU bits beyond the actual hard
    system limit.

(4) Future kernel versions may not even have a fixed CPU set size.

After the removal of the probing code, the kernel still returns
EINVAL if no CPU in the requested set remains which can run the
thread after the affinity change.

Applications which care about the exact affinity mask will have
to query it using sched_getaffinity after setting it.  Due to the
effects described above, this commit does not change this.

The new tests supersede tst-getcpu, which is removed.  This
addresses bug 19164 because the new tests allocate CPU sets
dynamically.

	* nptl/check-cpuset.h: Remove.
	* nptl/pthread_attr_setaffinity.c (__pthread_attr_setaffinity_new):
	Remove CPU set size check.
	* nptl/pthread_setattr_default_np.c (pthread_setattr_default_np):
	Likewise.
	* sysdeps/unix/sysv/linux/check-cpuset.h: Remove.
	* sysdeps/unix/sysv/linux/pthread_setaffinity.c
	(__kernel_cpumask_size, __determine_cpumask_size): Remove.
	(__pthread_setaffinity_new): Remove CPU set size check.
	* sysdeps/unix/sysv/linux/sched_setaffinity.c
	(__kernel_cpumask_size): Remove.
	(__sched_setaffinity_new): Remove CPU set size check.
	* manual/threads.texi (Default Thread Attributes): Remove stale
	reference to check_cpuset_attr, determine_cpumask_size in comment.
	* sysdeps/unix/sysv/linux/Makefile [$(subdir) == posix] (tests):
	Remove tst-getcpu.  Add tst-affinity, tst-affinity-pid.
	[$(subdir) == nptl] (tests): Add tst-thread-affinity-pthread,
	tst-thread-affinity-pthread2, tst-thread-affinity-sched.
	* sysdeps/unix/sysv/linux/tst-affinity.c: New file.
	* sysdeps/unix/sysv/linux/tst-affinity-pid.c: New file.
	* sysdeps/unix/sysv/linux/tst-skeleton-affinity.c: New skeleton test file.
	* sysdeps/unix/sysv/linux/tst-thread-affinity-sched.c: New file.
	* sysdeps/unix/sysv/linux/tst-thread-affinity-pthread.c: New file.
	* sysdeps/unix/sysv/linux/tst-thread-affinity-pthread2.c: New file.
	* sysdeps/unix/sysv/linux/tst-thread-skeleton-affinity.c: New
	skeleton test file.
	* sysdeps/unix/sysv/linux/tst-getcpu.c: Remove.  Superseded by
	tst-affinity-pid.

1 files changed, 95 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-thread-affinity-pthread2.c b/sysdeps/unix/sysv/linux/tst-thread-affinity-pthread2.c
new file mode 100644
index 0000000000..21cc9ae954
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-thread-affinity-pthread2.c
@@ -0,0 +1,95 @@
+/* Separate thread test for pthread_getaffinity_np, pthread_setaffinity_np.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* Defined for the benefit of tst-skeleton-thread-affinity.c, included
+   below.  This variant runs the functions on a separate thread.  */
+
+struct affinity_access_task
+{
+  pthread_t thread;
+  cpu_set_t *set;
+  size_t size;
+  bool get;
+  int result;
+};
+
+static void *
+affinity_access_thread (void *closure)
+{
+  struct affinity_access_task *task = closure;
+  if (task->get)
+    task->result = pthread_getaffinity_np
+      (task->thread, task->size, task->set);
+  else
+    task->result = pthread_setaffinity_np
+      (task->thread, task->size, task->set);
+  return NULL;
+}
+
+static int
+run_affinity_access_thread (cpu_set_t *set, size_t size, bool get)
+{
+  struct affinity_access_task task =
+    {
+      .thread = pthread_self (),
+      .set = set,
+      .size = size,
+      .get = get
+    };
+  pthread_t thr;
+  int ret = pthread_create (&thr, NULL, affinity_access_thread, &task);
+  if (ret != 0)
+    {
+      errno = ret;
+      printf ("error: could not create affinity access thread: %m\n");
+      abort ();
+    }
+  ret = pthread_join (thr, NULL);
+  if (ret != 0)
+    {
+      errno = ret;
+      printf ("error: could not join affinity access thread: %m\n");
+      abort ();
+    }
+  if (task.result != 0)
+    {
+      errno = task.result;
+      return -1;
+    }
+  return 0;
+}
+
+static int
+setaffinity (size_t size, const cpu_set_t *set)
+{
+  return run_affinity_access_thread ((cpu_set_t *) set, size, false);
+}
+
+static int
+getaffinity (size_t size, cpu_set_t *set)
+{
+  return run_affinity_access_thread (set, size, true);
+}
+
+#include "tst-skeleton-thread-affinity.c"