Revert "Revert "More pthreads cleanup.""

This reverts commit 6f94de3ca4

(Doesn't try to increase the number of TLS slots; that leads to
an inability to boot. Adds more tests.)

Change-Id: Ia7d25ba3995219ed6e686463dbba80c95cc831ca

libc/bionic/pthread_setname_np.cpp

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <pthread.h>
+
+#include <fcntl.h>
+#include <stdio.h> // For snprintf.
+#include <sys/prctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "pthread_internal.h"
+#include "private/ErrnoRestorer.h"
+
+// This value is not exported by kernel headers.
+#define MAX_TASK_COMM_LEN 16
+#define TASK_COMM_FMT "/proc/self/task/%u/comm"
+
+int pthread_setname_np(pthread_t thread, const char* thread_name) {
+  ErrnoRestorer errno_restorer;
+
+  if (thread == 0 || thread_name == NULL) {
+    return EINVAL;
+  }
+
+  size_t thread_name_len = strlen(thread_name);
+  if (thread_name_len >= MAX_TASK_COMM_LEN) {
+    return ERANGE;
+  }
+
+  // Changing our own name is an easy special case.
+  if (thread == pthread_self()) {
+    return prctl(PR_SET_NAME, (unsigned long)thread_name, 0, 0, 0) ? errno : 0;
+  }
+
+  // Have to change another thread's name.
+  pthread_internal_t* t = reinterpret_cast<pthread_internal_t*>(thread);
+  char comm_name[sizeof(TASK_COMM_FMT) + 8];
+  snprintf(comm_name, sizeof(comm_name), TASK_COMM_FMT, (unsigned int) t->kernel_id);
+  int fd = open(comm_name, O_RDWR);
+  if (fd == -1) {
+    return errno;
+  }
+  ssize_t n = TEMP_FAILURE_RETRY(write(fd, thread_name, thread_name_len));
+  close(fd);
+
+  if (n < 0) {
+    return errno;
+  } else if ((size_t)n != thread_name_len) {
+    return EIO;
+  }
+  return 0;
+}