8368124: Show useful thread names in ASAN reports

Reviewed-by: dholmes, mbaesken

Author: tstuefe

src/hotspot/os/linux/os_linux.cpp

@@ -160,7 +160,6 @@ address   os::Linux::_initial_thread_stack_bottom = nullptr;
 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 
 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = nullptr;
-int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = nullptr;
 pthread_t os::Linux::_main_thread;
 bool os::Linux::_supports_fast_thread_cpu_time = false;
 const char * os::Linux::_libc_version = nullptr;
@@ -4371,10 +4370,6 @@ void os::init(void) {
   // _main_thread points to the thread that created/loaded the JVM.
   Linux::_main_thread = pthread_self();
 
-  // retrieve entry point for pthread_setname_np
-  Linux::_pthread_setname_np =
-    (int(*)(pthread_t, const char*))dlsym(RTLD_DEFAULT, "pthread_setname_np");
-
   check_pax();
 
   // Check the availability of MADV_POPULATE_WRITE.
@@ -4851,14 +4846,24 @@ uint os::processor_id() {
 }
 
 void os::set_native_thread_name(const char *name) {
-  if (Linux::_pthread_setname_np) {
-    char buf [16]; // according to glibc manpage, 16 chars incl. '/0'
-    (void) os::snprintf(buf, sizeof(buf), "%s", name);
-    buf[sizeof(buf) - 1] = '\0';
-    const int rc = Linux::_pthread_setname_np(pthread_self(), buf);
-    // ERANGE should not happen; all other errors should just be ignored.
-    assert(rc != ERANGE, "pthread_setname_np failed");
-  }
+  char buf[16]; // according to glibc manpage, 16 chars incl. '/0'
+  // We may need to truncate the thread name. Since a common pattern
+  // for thread names is to be both longer than 15 chars and have a
+  // trailing number ("DispatcherWorkerThread21", "C2 CompilerThread#54" etc),
+  // we preserve the end of the thread name by truncating the middle
+  // (e.g. "Dispatc..read21").
+  const size_t len = strlen(name);
+  if (len < sizeof(buf)) {
+    strcpy(buf, name);
+  } else {
+    (void) os::snprintf(buf, sizeof(buf), "%.7s..%.6s", name, name + len - 6);
+  }
+  // Note: we use the system call here instead of calling pthread_setname_np
+  // since this is the only way to make ASAN aware of our thread names. Even
+  // though ASAN intercepts both prctl and pthread_setname_np, it only processes
+  // the thread name given to the former.
+  int rc = prctl(PR_SET_NAME, buf);
+  assert(rc == 0, "prctl(PR_SET_NAME) failed");
 }
 
 ////////////////////////////////////////////////////////////////////////////////

src/hotspot/os/linux/os_linux.hpp

@@ -33,7 +33,6 @@ class os::Linux {
   friend class os;
 
   static int (*_pthread_getcpuclockid)(pthread_t, clockid_t *);
-  static int (*_pthread_setname_np)(pthread_t, const char*);
 
   static address   _initial_thread_stack_bottom;
   static uintptr_t _initial_thread_stack_size;

src/hotspot/share/utilities/stringUtils.cpp

@@ -24,6 +24,7 @@
 
 #include "jvm_io.h"
 #include "memory/allocation.hpp"
+#include "runtime/os.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/stringUtils.hpp"
 

src/hotspot/share/utilities/stringUtils.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it

test/hotspot/gtest/runtime/test_os_linux.cpp

@@ -35,6 +35,7 @@
 #include "unittest.hpp"
 
 #include <sys/mman.h>
+#include <sys/prctl.h>
 
 static bool using_explicit_hugepages()  { return UseLargePages && !UseTransparentHugePages; }
 
@@ -468,4 +469,27 @@ TEST_VM(os_linux, glibc_mallinfo_wrapper) {
 #endif // ADDRESS_SANITIZER
 #endif // __GLIBC__
 
+static void test_set_thread_name(const char* name, const char* expected) {
+  os::set_native_thread_name(name);
+  char buf[16];
+  int rc = prctl(PR_GET_NAME, buf);
+  ASSERT_EQ(0, rc);
+  ASSERT_STREQ(buf, expected);
+}
+
+TEST_VM(os_linux, set_thread_name) {
+  char buf[16];
+  // retrieve current name
+  int rc = prctl(PR_GET_NAME, buf);
+  ASSERT_EQ(0, rc);
+
+  test_set_thread_name("shortname", "shortname");
+  test_set_thread_name("012345678901234",  "012345678901234");
+  test_set_thread_name("0123456789012345", "0123456..012345");
+  test_set_thread_name("MyAllocationWorkerThread22", "MyAlloc..read22");
+
+  // restore current name
+  test_set_thread_name(buf, buf);
+}
+
 #endif // LINUX