posix: set thread names

base/platform_thread_posix.cc

Index: base/platform_thread_posix.cc
diff --git a/base/platform_thread_posix.cc b/base/platform_thread_posix.cc
index 16fd529418ca0a5d02a2c5dc645d8064ac32cdc4..040452eb497bdc2d4507055767bc6dde625df529 100644
--- a/base/platform_thread_posix.cc
+++ b/base/platform_thread_posix.cc
@@ -4,6 +4,7 @@
 
 #include "base/platform_thread.h"
 
+#include <dlfcn.h>
 #include <errno.h>
 #include <sched.h>
 
@@ -11,15 +12,21 @@
 #include <mach/mach.h>
 #include <sys/resource.h>
 #include <algorithm>
-#else
+#endif
+
+#if defined(OS_LINUX)
+#include <sys/prctl.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 #endif
 
+#include "base/logging.h"
+#include "base/safe_strerror_posix.h"
+
 #if defined(OS_MACOSX)
 namespace base {
 void InitThreading();
-}  // namespace
+}  // namespace base
 #endif
 
 static void* ThreadFunc(void* closure) {
@@ -63,15 +70,50 @@ void PlatformThread::Sleep(int duration_ms) {
     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)
+// static
+void PlatformThread::SetName(const char* name) {
+  // 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) {
+    // 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)
+      LOG(ERROR) << "pthread_setname_np: " << safe_strerror(err);
+  } else {
+    // Implementing this function without glibc is simple enough.  (We
+    // don't do the name length clipping as above because it will be
+    // truncated by the callee (see TASK_COMM_LEN above).)
+    int err = prctl(PR_SET_NAME, name);
+    if (err < 0)
+      PLOG(ERROR) << "prctl(PR_SET_NAME)";
+  }
+}
+#elif defined(OS_MACOSX)
+// Mac is implemented in platform_thread_mac.mm.
+#else
 // static
 void PlatformThread::SetName(const char* name) {
-  // The POSIX standard does not provide for naming threads, and neither Linux
-  // nor Mac OS X (our two POSIX targets) provide any non-portable way of doing
-  // it either. (Some BSDs provide pthread_set_name_np but that isn't much of a
-  // consolation prize.)
-  // TODO(darin): decide whether stuffing the name in TLS or other in-memory
-  // structure would be useful for debugging or not.
+  // Leave it unimplemented.
+
+  // (This should be relatively simple to implement for the BSDs; I
+  // just don't have one handy to test the code on.)
 }
+#endif  // defined(OS_LINUX)
 
 namespace {