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, 278 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c b/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c
new file mode 100644
index 0000000000..8b8347d8d1
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c
@@ -0,0 +1,278 @@
+/* Generic test case for CPU affinity functions.
+   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/>.  */
+
+/* This file is included by the tst-affinity*.c files to test the two
+   variants of the functions, under different conditions.  The
+   following functions have to be definied:
+
+   static int getaffinity (size_t, cpu_set_t *);
+   static int setaffinity (size_t, const cpu_set_t *);
+   static bool early_test (struct conf *);
+
+   The first two functions shall affect the affinity mask for the
+   current thread and return 0 for success, -1 for error (with an
+   error code in errno).
+
+   early_test is invoked before the tests in this file affect the
+   affinity masks.  If it returns true, testing continues, otherwise
+   no more tests run and the overall test exits with status 1.
+*/
+
+#include <errno.h>
+#include <limits.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+/* CPU set configuration determined.  Can be used from early_test.  */
+struct conf
+{
+  int set_size;			/* in bits */
+  int last_cpu;
+};
+
+static int
+find_set_size (void)
+{
+  /* There is considerable controversy about how to determine the size
+     of the kernel CPU mask.  The probing loop below is only intended
+     for testing purposes.  */
+  for (int num_cpus = 64; num_cpus <= INT_MAX / 2; ++num_cpus)
+    {
+      cpu_set_t *set = CPU_ALLOC (num_cpus);
+      size_t size = CPU_ALLOC_SIZE (num_cpus);
+
+      if (set == NULL)
+	{
+	  printf ("error: CPU_ALLOC (%d) failed\n", num_cpus);
+	  return -1;
+	}
+      if (getaffinity (size, set) == 0)
+	{
+	  CPU_FREE (set);
+	  return num_cpus;
+	}
+      if (errno != EINVAL)
+	{
+	  printf ("error: getaffinity for %d CPUs: %m\n", num_cpus);
+	  CPU_FREE (set);
+	  return -1;
+	}
+      CPU_FREE (set);
+    }
+  puts ("error: Cannot find maximum CPU number");
+  return -1;
+}
+
+static int
+find_last_cpu (const cpu_set_t *set, size_t size)
+{
+  /* We need to determine the set size with CPU_COUNT_S and the
+     cpus_found counter because there is no direct way to obtain the
+     actual CPU set size, in bits, from the value of
+     CPU_ALLOC_SIZE.  */
+  size_t cpus_found = 0;
+  size_t total_cpus = CPU_COUNT_S (size, set);
+  int last_cpu = -1;
+
+  for (int cpu = 0; cpus_found < total_cpus; ++cpu)
+    {
+      if (CPU_ISSET_S (cpu, size, set))
+	{
+	  last_cpu = cpu;
+	  ++cpus_found;
+	}
+    }
+  return last_cpu;
+}
+
+static void
+setup_conf (struct conf *conf)
+{
+  *conf = (struct conf) {-1, -1};
+  conf->set_size = find_set_size ();
+  if (conf->set_size > 0)
+    {
+      cpu_set_t *set = CPU_ALLOC (conf->set_size);
+
+      if (set == NULL)
+	{
+	  printf ("error: CPU_ALLOC (%d) failed\n", conf->set_size);
+	  CPU_FREE (set);
+	  return;
+	}
+      if (getaffinity (CPU_ALLOC_SIZE (conf->set_size), set) < 0)
+	{
+	  printf ("error: getaffinity failed: %m\n");
+	  CPU_FREE (set);
+	  return;
+	}
+      conf->last_cpu = find_last_cpu (set, CPU_ALLOC_SIZE (conf->set_size));
+      if (conf->last_cpu < 0)
+	puts ("info: No test CPU found");
+      CPU_FREE (set);
+    }
+}
+
+static bool
+test_size (const struct conf *conf, size_t size)
+{
+  if (size < conf->set_size)
+    {
+      printf ("info: Test not run for CPU set size %zu\n", size);
+      return true;
+    }
+
+  cpu_set_t *initial_set = CPU_ALLOC (size);
+  cpu_set_t *set2 = CPU_ALLOC (size);
+  cpu_set_t *active_cpu_set = CPU_ALLOC (size);
+
+  if (initial_set == NULL || set2 == NULL || active_cpu_set == NULL)
+    {
+      printf ("error: size %zu: CPU_ALLOC failed\n", size);
+      return false;
+    }
+  size_t kernel_size = CPU_ALLOC_SIZE (size);
+
+  if (getaffinity (kernel_size, initial_set) < 0)
+    {
+      printf ("error: size %zu: getaffinity: %m\n", size);
+      return false;
+    }
+  if (setaffinity (kernel_size, initial_set) < 0)
+    {
+      printf ("error: size %zu: setaffinity: %m\n", size);
+      return true;
+    }
+
+  /* Use one-CPU set to test switching between CPUs.  */
+  int last_active_cpu = -1;
+  for (int cpu = 0; cpu <= conf->last_cpu; ++cpu)
+    {
+      int active_cpu = sched_getcpu ();
+      if (last_active_cpu >= 0 && last_active_cpu != active_cpu)
+	{
+	  printf ("error: Unexpected CPU %d, expected %d\n",
+		  active_cpu, last_active_cpu);
+	  return false;
+	}
+
+      if (!CPU_ISSET_S (cpu, kernel_size, initial_set))
+	continue;
+      last_active_cpu = cpu;
+
+      CPU_ZERO_S (kernel_size, active_cpu_set);
+      CPU_SET_S (cpu, kernel_size, active_cpu_set);
+      if (setaffinity (kernel_size, active_cpu_set) < 0)
+	{
+	  printf ("error: size %zu: setaffinity (%d): %m\n", size, cpu);
+	  return false;
+	}
+      active_cpu = sched_getcpu ();
+      if (active_cpu != cpu)
+	{
+	  printf ("error: Unexpected CPU %d, expected %d\n", active_cpu, cpu);
+	  return false;
+	}
+      if (getaffinity (kernel_size, set2) < 0)
+	{
+	  printf ("error: size %zu: getaffinity (2): %m\n", size);
+	  return false;
+	}
+      if (!CPU_EQUAL_S (kernel_size, active_cpu_set, set2))
+	{
+	  printf ("error: size %zu: CPU sets do not match\n", size);
+	  return false;
+	}
+    }
+
+  /* Test setting the all-ones set.  */
+  for (int cpu = 0; cpu < size; ++cpu)
+    CPU_SET_S (cpu, kernel_size, set2);
+  if (setaffinity (kernel_size, set2) < 0)
+    {
+      printf ("error: size %zu: setaffinity (3): %m\n", size);
+      return false;
+    }
+
+  if (setaffinity (kernel_size, initial_set) < 0)
+    {
+      printf ("error: size %zu: setaffinity (4): %m\n", size);
+      return false;
+    }
+  if (getaffinity (kernel_size, set2) < 0)
+    {
+      printf ("error: size %zu: getaffinity (3): %m\n", size);
+      return false;
+    }
+  if (!CPU_EQUAL_S (kernel_size, initial_set, set2))
+    {
+      printf ("error: size %zu: CPU sets do not match (2)\n", size);
+      return false;
+    }
+
+  CPU_FREE (initial_set);
+  CPU_FREE (set2);
+  CPU_FREE (active_cpu_set);
+
+  return true;
+}
+
+static int
+do_test (void)
+{
+  {
+    cpu_set_t set;
+    if (getaffinity (sizeof (set), &set) < 0 && errno == ENOSYS)
+      {
+	puts ("warning: getaffinity not supported, test cannot run");
+	return 0;
+      }
+    if (sched_getcpu () < 0 && errno == ENOSYS)
+      {
+	puts ("warning: sched_getcpu not supported, test cannot run");
+	return 0;
+      }
+  }
+
+  struct conf conf;
+  setup_conf (&conf);
+  printf ("info: Detected CPU set size (in bits): %d\n", conf.set_size);
+  printf ("info: Maximum test CPU: %d\n", conf.last_cpu);
+  if (conf.set_size < 0 || conf.last_cpu < 0)
+    return 1;
+
+  if (!early_test (&conf))
+    return 1;
+
+  bool error = false;
+  error |= !test_size (&conf, 1024);
+  error |= !test_size (&conf, conf.set_size);
+  error |= !test_size (&conf, 2);
+  error |= !test_size (&conf, 32);
+  error |= !test_size (&conf, 40);
+  error |= !test_size (&conf, 64);
+  error |= !test_size (&conf, 96);
+  error |= !test_size (&conf, 128);
+  error |= !test_size (&conf, 256);
+  error |= !test_size (&conf, 8192);
+  return error;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"