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, 201 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-affinity-pid.c b/sysdeps/unix/sysv/linux/tst-affinity-pid.c
new file mode 100644
index 0000000000..309f1add6a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-affinity-pid.c
@@ -0,0 +1,201 @@
+/* Test for sched_getaffinity and sched_setaffinity, PID version.
+   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/>.  */
+
+/* Function definitions for the benefit of tst-skeleton-affinity.c.
+   This variant forks a child process which then invokes
+   sched_getaffinity and sched_setaffinity on the parent PID.  */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static int
+write_fully (int fd, const void *buffer, size_t length)
+{
+  const void *end = buffer + length;
+  while (buffer < end)
+    {
+      ssize_t bytes_written = TEMP_FAILURE_RETRY
+        (write (fd, buffer, end - buffer));
+      if (bytes_written < 0)
+        return -1;
+      if (bytes_written == 0)
+        {
+          errno = ENOSPC;
+          return -1;
+        }
+      buffer += bytes_written;
+    }
+  return 0;
+}
+
+static ssize_t
+read_fully (int fd, void *buffer, size_t length)
+{
+  const void *start = buffer;
+  const void *end = buffer + length;
+  while (buffer < end)
+    {
+      ssize_t bytes_read = TEMP_FAILURE_RETRY
+        (read (fd, buffer, end - buffer));
+      if (bytes_read < 0)
+        return -1;
+      if (bytes_read == 0)
+        return buffer - start;
+      buffer += bytes_read;
+    }
+  return length;
+}
+
+static int
+process_child_response (int *pipes, pid_t child,
+                        cpu_set_t *set, size_t size)
+{
+  close (pipes[1]);
+
+  int value_from_child;
+  ssize_t bytes_read = read_fully
+    (pipes[0], &value_from_child, sizeof (value_from_child));
+  if (bytes_read < 0)
+    {
+      printf ("error: read from child: %m\n");
+      exit (1);
+    }
+  if (bytes_read != sizeof (value_from_child))
+    {
+      printf ("error: not enough bytes from child: %zd\n", bytes_read);
+      exit (1);
+    }
+  if (value_from_child == 0)
+    {
+      bytes_read = read_fully (pipes[0], set, size);
+      if (bytes_read < 0)
+        {
+          printf ("error: read: %m\n");
+          exit (1);
+        }
+      if (bytes_read != size)
+        {
+          printf ("error: not enough bytes from child: %zd\n", bytes_read);
+          exit (1);
+        }
+    }
+
+  int status;
+  if (waitpid (child, &status, 0) < 0)
+    {
+      printf ("error: waitpid: %m\n");
+      exit (1);
+    }
+  if (!(WIFEXITED (status) && WEXITSTATUS (status) == 0))
+    {
+      printf ("error: invalid status from : %m\n");
+      exit (1);
+    }
+
+  close (pipes[0]);
+
+  if (value_from_child != 0)
+    {
+      errno = value_from_child;
+      return -1;
+    }
+  return 0;
+}
+
+static int
+getaffinity (size_t size, cpu_set_t *set)
+{
+  int pipes[2];
+  if (pipe (pipes) < 0)
+    {
+      printf ("error: pipe: %m\n");
+      exit (1);
+    }
+
+  int ret = fork ();
+  if (ret < 0)
+    {
+      printf ("error: fork: %m\n");
+      exit (1);
+    }
+  if (ret == 0)
+    {
+      /* Child.  */
+      int ret = sched_getaffinity (getppid (), size, set);
+      if (ret < 0)
+        ret = errno;
+      if (write_fully (pipes[1], &ret, sizeof (ret)) < 0
+          || write_fully (pipes[1], set, size) < 0
+          || (ret == 0 && write_fully (pipes[1], set, size) < 0))
+        {
+          printf ("error: write: %m\n");
+          _exit (1);
+        }
+      _exit (0);
+    }
+
+  /* Parent.  */
+  return process_child_response (pipes, ret, set, size);
+}
+
+static int
+setaffinity (size_t size, const cpu_set_t *set)
+{
+  int pipes[2];
+  if (pipe (pipes) < 0)
+    {
+      printf ("error: pipe: %m\n");
+      exit (1);
+    }
+
+  int ret = fork ();
+  if (ret < 0)
+    {
+      printf ("error: fork: %m\n");
+      exit (1);
+    }
+  if (ret == 0)
+    {
+      /* Child.  */
+      int ret = sched_setaffinity (getppid (), size, set);
+      if (write_fully (pipes[1], &ret, sizeof (ret)) < 0)
+        {
+          printf ("error: write: %m\n");
+          _exit (1);
+        }
+      _exit (0);
+    }
+
+  /* Parent.  There is no affinity mask to read from the child, so the
+     size is 0.  */
+  return process_child_response (pipes, ret, NULL, 0);
+}
+
+struct conf;
+static bool early_test (struct conf *unused)
+{
+  return true;
+}
+
+#include "tst-skeleton-affinity.c"