8189170: Add option to disable stack overflow checking in primordial thread for use with JNI_CreateJavaJVM

Reviewed-by: stuefe, dcubed

src/hotspot/os/aix/os_aix.cpp

@@ -399,7 +399,7 @@ static void query_multipage_support() {
   // thread (because primordial thread's stack may have different page size than
   // pthread thread stacks). Running a VM on the primordial thread won't work for a
   // number of reasons so we may just as well guarantee it here.
-  guarantee0(!os::Aix::is_primordial_thread());
+  guarantee0(!os::is_primordial_thread());
 
   // Query pthread stack page size. Should be the same as data page size because
   // pthread stacks are allocated from C-Heap.
@@ -3448,7 +3448,7 @@ void os::init(void) {
 
   init_random(1234567);
 
-  // Main_thread points to the aboriginal thread.
+  // _main_thread points to the thread that created/loaded the JVM.
   Aix::_main_thread = pthread_self();
 
   initial_time_count = os::elapsed_counter();
@@ -3995,7 +3995,7 @@ void os::pause() {
   }
 }
 
-bool os::Aix::is_primordial_thread() {
+bool os::is_primordial_thread(void) {
   if (pthread_self() == (pthread_t)1) {
     return true;
   } else {

src/hotspot/os/aix/os_aix.hpp

@@ -99,12 +99,6 @@ class Aix {
   // Given an address, returns the size of the page backing that address
   static size_t query_pagesize(void* p);
 
-  // Return `true' if the calling thread is the primordial thread. The
-  // primordial thread is the thread which contains the main function,
-  // *not* necessarily the thread which initialized the VM by calling
-  // JNI_CreateJavaVM.
-  static bool is_primordial_thread(void);
-
   static int page_size(void) {
     assert(_page_size != -1, "not initialized");
     return _page_size;

src/hotspot/os/bsd/os_bsd.cpp

@@ -3360,7 +3360,7 @@ void os::init(void) {
 
   Bsd::initialize_system_info();
 
-  // main_thread points to the aboriginal thread
+  // _main_thread points to the thread that created/loaded the JVM.
   Bsd::_main_thread = pthread_self();
 
   Bsd::clock_init();

src/hotspot/os/bsd/os_bsd.hpp

@@ -74,7 +74,6 @@ class Bsd {
 
   static void hotspot_sigmask(Thread* thread);
 
-  static bool is_initial_thread(void);
   static pid_t gettid();
 
   static int page_size(void)                                        { return _page_size; }

src/hotspot/os/linux/os_linux.cpp

@@ -853,8 +853,8 @@ bool os::create_attached_thread(JavaThread* thread) {
     }
   }
 
-  if (os::Linux::is_initial_thread()) {
-    // If current thread is initial thread, its stack is mapped on demand,
+  if (os::is_primordial_thread()) {
+    // If current thread is primordial thread, its stack is mapped on demand,
     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
     // the entire stack region to avoid SEGV in stack banging.
     // It is also useful to get around the heap-stack-gap problem on SuSE
@@ -915,19 +915,20 @@ void os::free_thread(OSThread* osthread) {
 }
 
 //////////////////////////////////////////////////////////////////////////////
-// initial thread
+// primordial thread
 
-// Check if current thread is the initial thread, similar to Solaris thr_main.
-bool os::Linux::is_initial_thread(void) {
+// Check if current thread is the primordial thread, similar to Solaris thr_main.
+bool os::is_primordial_thread(void) {
   char dummy;
   // If called before init complete, thread stack bottom will be null.
   // Can be called if fatal error occurs before initialization.
-  if (initial_thread_stack_bottom() == NULL) return false;
-  assert(initial_thread_stack_bottom() != NULL &&
-         initial_thread_stack_size()   != 0,
-         "os::init did not locate initial thread's stack region");
-  if ((address)&dummy >= initial_thread_stack_bottom() &&
-      (address)&dummy < initial_thread_stack_bottom() + initial_thread_stack_size()) {
+  if (os::Linux::initial_thread_stack_bottom() == NULL) return false;
+  assert(os::Linux::initial_thread_stack_bottom() != NULL &&
+         os::Linux::initial_thread_stack_size()   != 0,
+         "os::init did not locate primordial thread's stack region");
+  if ((address)&dummy >= os::Linux::initial_thread_stack_bottom() &&
+      (address)&dummy < os::Linux::initial_thread_stack_bottom() +
+                        os::Linux::initial_thread_stack_size()) {
     return true;
   } else {
     return false;
@@ -958,7 +959,7 @@ static bool find_vma(address addr, address* vma_low, address* vma_high) {
   return false;
 }
 
-// Locate initial thread stack. This special handling of initial thread stack
+// Locate primordial thread stack. This special handling of primordial thread stack
 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
 // bogus value for the primordial process thread. While the launcher has created
 // the VM in a new thread since JDK 6, we still have to allow for the use of the
@@ -982,7 +983,10 @@ void os::Linux::capture_initial_stack(size_t max_size) {
   // 6308388: a bug in ld.so will relocate its own .data section to the
   //   lower end of primordial stack; reduce ulimit -s value a little bit
   //   so we won't install guard page on ld.so's data section.
-  stack_size -= 2 * page_size();
+  //   But ensure we don't underflow the stack size - allow 1 page spare
+  if (stack_size >= (size_t)(3 * page_size())) {
+    stack_size -= 2 * page_size();
+  }
 
   // Try to figure out where the stack base (top) is. This is harder.
   //
@@ -1103,16 +1107,16 @@ void os::Linux::capture_initial_stack(size_t max_size) {
 
       if (i != 28 - 2) {
         assert(false, "Bad conversion from /proc/self/stat");
-        // product mode - assume we are the initial thread, good luck in the
+        // product mode - assume we are the primordial thread, good luck in the
         // embedded case.
-        warning("Can't detect initial thread stack location - bad conversion");
+        warning("Can't detect primordial thread stack location - bad conversion");
         stack_start = (uintptr_t) &rlim;
       }
     } else {
       // For some reason we can't open /proc/self/stat (for example, running on
       // FreeBSD with a Linux emulator, or inside chroot), this should work for
       // most cases, so don't abort:
-      warning("Can't detect initial thread stack location - no /proc/self/stat");
+      warning("Can't detect primordial thread stack location - no /proc/self/stat");
       stack_start = (uintptr_t) &rlim;
     }
   }
@@ -1132,7 +1136,7 @@ void os::Linux::capture_initial_stack(size_t max_size) {
     stack_top = (uintptr_t)high;
   } else {
     // failed, likely because /proc/self/maps does not exist
-    warning("Can't detect initial thread stack location - find_vma failed");
+    warning("Can't detect primordial thread stack location - find_vma failed");
     // best effort: stack_start is normally within a few pages below the real
     // stack top, use it as stack top, and reduce stack size so we won't put
     // guard page outside stack.
@@ -3136,10 +3140,10 @@ static address get_stack_commited_bottom(address bottom, size_t size) {
 // where we're going to put our guard pages, truncate the mapping at
 // that point by munmap()ping it.  This ensures that when we later
 // munmap() the guard pages we don't leave a hole in the stack
-// mapping. This only affects the main/initial thread
+// mapping. This only affects the main/primordial thread
 
 bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
-  if (os::Linux::is_initial_thread()) {
+  if (os::is_primordial_thread()) {
     // As we manually grow stack up to bottom inside create_attached_thread(),
     // it's likely that os::Linux::initial_thread_stack_bottom is mapped and
     // we don't need to do anything special.
@@ -3164,14 +3168,14 @@ bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
 
 // If this is a growable mapping, remove the guard pages entirely by
 // munmap()ping them.  If not, just call uncommit_memory(). This only
-// affects the main/initial thread, but guard against future OS changes
-// It's safe to always unmap guard pages for initial thread because we
-// always place it right after end of the mapped region
+// affects the main/primordial thread, but guard against future OS changes.
+// It's safe to always unmap guard pages for primordial thread because we
+// always place it right after end of the mapped region.
 
 bool os::remove_stack_guard_pages(char* addr, size_t size) {
   uintptr_t stack_extent, stack_base;
 
-  if (os::Linux::is_initial_thread()) {
+  if (os::is_primordial_thread()) {
     return ::munmap(addr, size) == 0;
   }
 
@@ -4860,10 +4864,9 @@ void os::Linux::check_signal_handler(int sig) {
 extern void report_error(char* file_name, int line_no, char* title,
                          char* format, ...);
 
-// this is called _before_ the most of global arguments have been parsed
+// this is called _before_ most of the global arguments have been parsed
 void os::init(void) {
   char dummy;   // used to get a guess on initial stack address
-//  first_hrtime = gethrtime();
 
   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
 
@@ -4880,7 +4883,7 @@ void os::init(void) {
 
   Linux::initialize_os_info();
 
-  // main_thread points to the aboriginal thread
+  // _main_thread points to the thread that created/loaded the JVM.
   Linux::_main_thread = pthread_self();
 
   Linux::clock_init();
@@ -5851,8 +5854,8 @@ bool os::start_debugging(char *buf, int buflen) {
 //
 #ifndef ZERO
 static void current_stack_region(address * bottom, size_t * size) {
-  if (os::Linux::is_initial_thread()) {
-    // initial thread needs special handling because pthread_getattr_np()
+  if (os::is_primordial_thread()) {
+    // primordial thread needs special handling because pthread_getattr_np()
     // may return bogus value.
     *bottom = os::Linux::initial_thread_stack_bottom();
     *size   = os::Linux::initial_thread_stack_size();

src/hotspot/os/linux/os_linux.hpp

@@ -132,7 +132,6 @@ class Linux {
 
   static address   initial_thread_stack_bottom(void)                { return _initial_thread_stack_bottom; }
   static uintptr_t initial_thread_stack_size(void)                  { return _initial_thread_stack_size; }
-  static bool is_initial_thread(void);
 
   static int page_size(void)                                        { return _page_size; }
   static void set_page_size(int val)                                { _page_size = val; }

src/hotspot/os/solaris/os_solaris.cpp

@@ -200,17 +200,21 @@ static inline stack_t get_stack_info() {
   return st;
 }
 
-address os::current_stack_base() {
+bool os::is_primordial_thread(void) {
   int r = thr_main();
   guarantee(r == 0 || r == 1, "CR6501650 or CR6493689");
-  bool is_primordial_thread = r;
+  return r == 1;
+}
+
+address os::current_stack_base() {
+  bool _is_primordial_thread = is_primordial_thread();
 
   // Workaround 4352906, avoid calls to thr_stksegment by
   // thr_main after the first one (it looks like we trash
   // some data, causing the value for ss_sp to be incorrect).
-  if (!is_primordial_thread || os::Solaris::_main_stack_base == NULL) {
+  if (!_is_primordial_thread || os::Solaris::_main_stack_base == NULL) {
     stack_t st = get_stack_info();
-    if (is_primordial_thread) {
+    if (_is_primordial_thread) {
       // cache initial value of stack base
       os::Solaris::_main_stack_base = (address)st.ss_sp;
     }
@@ -224,9 +228,7 @@ address os::current_stack_base() {
 size_t os::current_stack_size() {
   size_t size;
 
-  int r = thr_main();
-  guarantee(r == 0 || r == 1, "CR6501650 or CR6493689");
-  if (!r) {
+  if (!is_primordial_thread()) {
     size = get_stack_info().ss_size;
   } else {
     struct rlimit limits;
@@ -1102,9 +1104,7 @@ void _handle_uncaught_cxx_exception() {
 
 // First crack at OS-specific initialization, from inside the new thread.
 void os::initialize_thread(Thread* thr) {
-  int r = thr_main();
-  guarantee(r == 0 || r == 1, "CR6501650 or CR6493689");
-  if (r) {
+  if (is_primordial_thread()) {
     JavaThread* jt = (JavaThread *)thr;
     assert(jt != NULL, "Sanity check");
     size_t stack_size;
@@ -4203,6 +4203,7 @@ void os::init(void) {
     dladdr1_func = CAST_TO_FN_PTR(dladdr1_func_type, dlsym(hdl, "dladdr1"));
   }
 
+  // main_thread points to the thread that created/loaded the JVM.
   main_thread = thr_self();
 
   // dynamic lookup of functions that may not be available in our lowest

src/hotspot/share/gc/shared/threadLocalAllocBuffer.cpp

@@ -193,7 +193,7 @@ void ThreadLocalAllocBuffer::initialize() {
 
   set_desired_size(initial_desired_size());
 
-  // Following check is needed because at startup the main (primordial)
+  // Following check is needed because at startup the main
   // thread is initialized before the heap is.  The initialization for
   // this thread is redone in startup_initialization below.
   if (Universe::heap() != NULL) {
@@ -240,7 +240,7 @@ void ThreadLocalAllocBuffer::startup_initialization() {
   }
 #endif
 
-  // During jvm startup, the main (primordial) thread is initialized
+  // During jvm startup, the main thread is initialized
   // before the heap is initialized.  So reinitialize it now.
   guarantee(Thread::current()->is_Java_thread(), "tlab initialization thread not Java thread");
   Thread::current()->tlab().initialize();

src/hotspot/share/runtime/globals.hpp

@@ -1178,6 +1178,10 @@ public:
           "Use detached threads that are recycled upon termination "        \
           "(for Solaris only)")                                             \
                                                                             \
+  experimental(bool, DisablePrimordialThreadGuardPages, false,              \
+               "Disable the use of stack guard pages if the JVM is loaded " \
+               "on the primordial process thread")                          \
+                                                                            \
   product(bool, UseLWPSynchronization, true,                                \
           "Use LWP-based instead of libthread-based synchronization "       \
           "(SPARC only)")                                                   \

src/hotspot/share/runtime/os.hpp

@@ -454,7 +454,24 @@ class os: AllStatic {
   static bool create_thread(Thread* thread,
                             ThreadType thr_type,
                             size_t req_stack_size = 0);
+
+  // The "main thread", also known as "starting thread", is the thread
+  // that loads/creates the JVM via JNI_CreateJavaVM.
   static bool create_main_thread(JavaThread* thread);
+
+  // The primordial thread is the initial process thread. The java
+  // launcher never uses the primordial thread as the main thread, but
+  // applications that host the JVM directly may do so. Some platforms
+  // need special-case handling of the primordial thread if it attaches
+  // to the VM.
+  static bool is_primordial_thread(void)
+#if defined(_WINDOWS) || defined(BSD)
+    // No way to identify the primordial thread.
+    { return false; }
+#else
+  ;
+#endif
+
   static bool create_attached_thread(JavaThread* thread);
   static void pd_start_thread(Thread* thread);
   static void start_thread(Thread* thread);

src/hotspot/share/runtime/thread.cpp

@@ -2471,7 +2471,13 @@ size_t JavaThread::_stack_reserved_zone_size = 0;
 size_t JavaThread::_stack_shadow_zone_size = 0;
 
 void JavaThread::create_stack_guard_pages() {
-  if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
+  if (!os::uses_stack_guard_pages() ||
+      _stack_guard_state != stack_guard_unused ||
+      (DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
+      log_info(os, thread)("Stack guard page creation for thread "
+                           UINTX_FORMAT " disabled", os::current_thread_id());
+    return;
+  }
   address low_addr = stack_end();
   size_t len = stack_guard_zone_size();
 

src/hotspot/share/runtime/thread.inline.hpp

@@ -156,7 +156,8 @@ inline size_t JavaThread::stack_available(address cur_sp) {
 
 inline bool JavaThread::stack_guards_enabled() {
 #ifdef ASSERT
-  if (os::uses_stack_guard_pages()) {
+  if (os::uses_stack_guard_pages() &&
+      !(DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
     assert(_stack_guard_state != stack_guard_unused, "guard pages must be in use");
   }
 #endif