Enable setting thread names on Linux

base/threading/platform_thread_posix.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <sched.h>
 
 #include "base/lazy_instance.h"
@@ skipping 148 matching lines @@
   sleep_time.tv_sec = duration_ms / 1000;
   duration_ms -= sleep_time.tv_sec * 1000;
 
   // Contains the portion of duration_ms < 1 sec.
   sleep_time.tv_nsec = duration_ms * 1000 * 1000;  // nanoseconds.
 
   while (nanosleep(&sleep_time, &remaining) == -1 && errno == EINTR)
     sleep_time = remaining;
 }
 
-// Linux SetName is currently disabled, as we need to distinguish between
-// helper threads (where it's ok to make this call) and the main thread
-// (where making this call renames our process, causing tools like killall
-// to stop working).
-#if 0 && defined(OS_LINUX)
+#if defined(OS_LINUX)
 // static
 void PlatformThread::SetName(const char* name) {
   // have to cast away const because ThreadLocalPointer does not support const
   // void*
   current_thread_name.Pointer()->Set(const_cast<char*>(name));
   tracked_objects::ThreadData::InitializeThreadContext(name);
 
+  // On linux we can get the thread names to show up in the debugger by setting
+  // the process name for the LWP.  We don't want to do this for the main
+  // thread because that would rename the process, causing tools like killall
+  // to stop working.
+  if (PlatformThread::CurrentId() == getpid())
+    return;
+
   // http://0pointer.de/blog/projects/name-your-threads.html
 
   // glibc recently added support for pthread_setname_np, but it's not
   // commonly available yet.  So test for it at runtime.
   int (*dynamic_pthread_setname_np)(pthread_t, const char*);
   *reinterpret_cast<void**>(&dynamic_pthread_setname_np) =
       dlsym(RTLD_DEFAULT, "pthread_setname_np");
 
   if (dynamic_pthread_setname_np) {

[Rick Byers, 2011/12/14 15:45:09]

What's the benefit of using this API at all?  Can't we just use prctl in all
cases (and then avoid the cost of the dynamic symbol lookup and extra complexity
of having two different code paths?).

     // This limit comes from glibc, which gets it from the kernel
     // (TASK_COMM_LEN).
     const int kMaxNameLength = 15;
     std::string shortened_name = std::string(name).substr(0, kMaxNameLength);
     int err = dynamic_pthread_setname_np(pthread_self(),
                                          shortened_name.c_str());
     if (err < 0)
       DLOG(ERROR) << "pthread_setname_np: " << safe_strerror(err);
   } else {
     // Implementing this function without glibc is simple enough.  (We
@@ skipping 57 matching lines @@
 // Mac OS X uses lower-level mach APIs
 
 // static
 void PlatformThread::SetThreadPriority(PlatformThreadHandle, ThreadPriority) {
   // TODO(crogers): implement
   NOTIMPLEMENTED();
 }
 #endif
 
 }  // namespace base