8150353: PPC64LE: Support RTM on linux

Reviewed-by: mdoerr, kvn

hotspot/src/cpu/ppc/vm/globalDefinitions_ppc.hpp

@@ -47,7 +47,7 @@ const bool CCallingConventionRequiresIntsAsLongs = true;
 // The expected size in bytes of a cache line, used to pad data structures.
 #define DEFAULT_CACHE_LINE_SIZE 128
 
-#if defined(COMPILER2) && defined(AIX)
+#if defined(COMPILER2) && (defined(AIX) || defined(linux))
 // Include Transactional Memory lock eliding optimization
 #define INCLUDE_RTM_OPT 1
 #endif

hotspot/src/cpu/ppc/vm/vm_version_ppc.cpp

@@ -255,7 +255,16 @@ void VM_Version::initialize() {
     }
 #endif
 #ifdef linux
-    // TODO: check kernel version (we currently have too old versions only)
+    // At least Linux kernel 4.2, as the problematic behavior of syscalls
+    // being called in the middle of a transaction has been addressed.
+    // Please, refer to commit b4b56f9ecab40f3b4ef53e130c9f6663be491894
+    // in Linux kernel source tree: https://goo.gl/Kc5i7A
+    if (os::Linux::os_version_is_known()) {
+      if (os::Linux::os_version() >= 0x040200)
+        os_too_old = false;
+    } else {
+      vm_exit_during_initialization("RTM can not be enabled: kernel version is unknown.");
+    }
 #endif
     if (os_too_old) {
       vm_exit_during_initialization("RTM is not supported on this OS version.");

hotspot/src/os/linux/vm/os_linux.cpp

@@ -144,6 +144,7 @@ pthread_t os::Linux::_main_thread;
 int os::Linux::_page_size = -1;
 const int os::Linux::_vm_default_page_size = (8 * K);
 bool os::Linux::_supports_fast_thread_cpu_time = false;
+uint32_t os::Linux::_os_version = 0;
 const char * os::Linux::_glibc_version = NULL;
 const char * os::Linux::_libpthread_version = NULL;
 pthread_condattr_t os::Linux::_condattr[1];
@@ -4356,6 +4357,48 @@ jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
   return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
 }
 
+void os::Linux::initialize_os_info() {
+  assert(_os_version == 0, "OS info already initialized");
+
+  struct utsname _uname;
+
+  uint32_t major;
+  uint32_t minor;
+  uint32_t fix;
+
+  int rc;
+
+  // Kernel version is unknown if
+  // verification below fails.
+  _os_version = 0x01000000;
+
+  rc = uname(&_uname);
+  if (rc != -1) {
+
+    rc = sscanf(_uname.release,"%d.%d.%d", &major, &minor, &fix);
+    if (rc == 3) {
+
+      if (major < 256 && minor < 256 && fix < 256) {
+        // Kernel version format is as expected,
+        // set it overriding unknown state.
+        _os_version = (major << 16) |
+                      (minor << 8 ) |
+                      (fix   << 0 ) ;
+      }
+    }
+  }
+}
+
+uint32_t os::Linux::os_version() {
+  assert(_os_version != 0, "not initialized");
+  return _os_version & 0x00FFFFFF;
+}
+
+bool os::Linux::os_version_is_known() {
+  assert(_os_version != 0, "not initialized");
+  return _os_version & 0x01000000 ? false : true;
+}
+
 /////
 // glibc on Linux platform uses non-documented flag
 // to indicate, that some special sort of signal
@@ -4578,6 +4621,8 @@ void os::init(void) {
 
   Linux::initialize_system_info();
 
+  Linux::initialize_os_info();
+
   // main_thread points to the aboriginal thread
   Linux::_main_thread = pthread_self();
 

hotspot/src/os/linux/vm/os_linux.hpp

@@ -56,6 +56,15 @@ class Linux {
 
   static GrowableArray<int>* _cpu_to_node;
 
+  // 0x00000000 = uninitialized,
+  // 0x01000000 = kernel version unknown,
+  // otherwise a 32-bit number:
+  // Ox00AABBCC
+  // AA, Major Version
+  // BB, Minor Version
+  // CC, Fix   Version
+  static uint32_t _os_version;
+
  protected:
 
   static julong _physical_memory;
@@ -198,6 +207,10 @@ class Linux {
 
   static jlong fast_thread_cpu_time(clockid_t clockid);
 
+  static void initialize_os_info();
+  static bool os_version_is_known();
+  static uint32_t os_version();
+
   // pthread_cond clock suppport
  private:
   static pthread_condattr_t _condattr[1];

hotspot/src/share/vm/opto/compile.hpp

@@ -1118,7 +1118,11 @@ class Compile : public Phase {
   bool           in_scratch_emit_size() const   { return _in_scratch_emit_size;     }
 
   enum ScratchBufferBlob {
+#if defined(PPC64)
+    MAX_inst_size       = 2048,
+#else
     MAX_inst_size       = 1024,
+#endif
     MAX_locs_size       = 128, // number of relocInfo elements
     MAX_const_size      = 128,
     MAX_stubs_size      = 128