Mercurial > hg > graal-jvmci-8

changeset 22807:9989538b7507

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Merge
author coffeys
date Wed, 21 Jan 2015 17:07:26 +0000
parents 6fe56d3026d5 (diff) 0ee548a1cda0 (current diff)
children 8a748ce0e308 5fa73007ceb9
files .hgtags make/hotspot_version src/share/vm/utilities/vmError.cpp
diffstat 22 files changed, 268 insertions(+), 58 deletions(-) [+]
line wrap: on
line diff
--- a/.hgtags	Tue Jan 20 13:47:31 2015 -0800
+++ b/.hgtags	Wed Jan 21 17:07:26 2015 +0000
@@ -584,3 +584,6 @@
 d2e9a6bec4f2eec8506eed16f7324992a85d8480 hs25.40-b24
 25ec4a67433744bbe3406e5069e7fd1876ebbf2f jdk8u40-b21
 0f0cb4eeab2d871274f4ffdcd6017d2fdfa89238 hs25.40-b25
+d9349fa8822336e0244da0a8448f3e6b2d62741d jdk8u60-b00
+d9349fa8822336e0244da0a8448f3e6b2d62741d hs25.60-b00
+ebf89088c08ab0508b9002b48dd3d68a340259af hs25.60-b01
--- a/make/hotspot_version	Tue Jan 20 13:47:31 2015 -0800
+++ b/make/hotspot_version	Wed Jan 21 17:07:26 2015 +0000
@@ -34,8 +34,8 @@
 HOTSPOT_VM_COPYRIGHT=Copyright 2015
 
 HS_MAJOR_VER=25
-HS_MINOR_VER=40
-HS_BUILD_NUMBER=25
+HS_MINOR_VER=60
+HS_BUILD_NUMBER=01
 
 JDK_MAJOR_VER=1
 JDK_MINOR_VER=8
--- a/src/cpu/ppc/vm/frame_ppc.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/ppc/vm/frame_ppc.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -318,3 +318,10 @@
   // unused... but returns fp() to minimize changes introduced by 7087445
   return fp();
 }
+
+#ifndef PRODUCT
+// This is a generic constructor which is only used by pns() in debug.cpp.
+frame::frame(void* sp, void* fp, void* pc) : _sp((intptr_t*)sp), _unextended_sp((intptr_t*)sp) {
+  find_codeblob_and_set_pc_and_deopt_state((address)pc); // also sets _fp and adjusts _unextended_sp
+}
+#endif
--- a/src/cpu/sparc/vm/frame_sparc.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/sparc/vm/frame_sparc.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -342,7 +342,7 @@
 // constructors
 
 // Construct an unpatchable, deficient frame
-frame::frame(intptr_t* sp, unpatchable_t, address pc, CodeBlob* cb) {
+void frame::init(intptr_t* sp, address pc, CodeBlob* cb) {
 #ifdef _LP64
   assert( (((intptr_t)sp & (wordSize-1)) == 0), "frame constructor passed an invalid sp");
 #endif
@@ -364,6 +364,10 @@
 #endif // ASSERT
 }
 
+frame::frame(intptr_t* sp, unpatchable_t, address pc, CodeBlob* cb) {
+  init(sp, pc, cb);
+}
+
 frame::frame(intptr_t* sp, intptr_t* younger_sp, bool younger_frame_is_interpreted) :
   _sp(sp),
   _younger_sp(younger_sp),
@@ -418,6 +422,13 @@
   }
 }
 
+#ifndef PRODUCT
+// This is a generic constructor which is only used by pns() in debug.cpp.
+frame::frame(void* sp, void* fp, void* pc) {
+  init((intptr_t*)sp, (address)pc, NULL);
+}
+#endif
+
 bool frame::is_interpreted_frame() const  {
   return Interpreter::contains(pc());
 }
--- a/src/cpu/sparc/vm/frame_sparc.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/sparc/vm/frame_sparc.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -164,6 +164,8 @@
   enum unpatchable_t { unpatchable };
   frame(intptr_t* sp, unpatchable_t, address pc = NULL, CodeBlob* cb = NULL);
 
+  void init(intptr_t* sp, address pc, CodeBlob* cb);
+
   // Walk from sp outward looking for old_sp, and return old_sp's predecessor
   // (i.e. return the sp from the frame where old_sp is the fp).
   // Register windows are assumed to be flushed for the stack in question.
--- a/src/cpu/x86/vm/frame_x86.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/x86/vm/frame_x86.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -717,3 +717,10 @@
   assert(! is_compiled_frame(), "unknown compiled frame size");
   return fp();
 }
+
+#ifndef PRODUCT
+// This is a generic constructor which is only used by pns() in debug.cpp.
+frame::frame(void* sp, void* fp, void* pc) {
+  init((intptr_t*)sp, (intptr_t*)fp, (address)pc);
+}
+#endif
--- a/src/cpu/x86/vm/frame_x86.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/x86/vm/frame_x86.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -187,6 +187,8 @@
 
   frame(intptr_t* sp, intptr_t* fp);
 
+  void init(intptr_t* sp, intptr_t* fp, address pc);
+
   // accessors for the instance variables
   // Note: not necessarily the real 'frame pointer' (see real_fp)
   intptr_t*   fp() const { return _fp; }
--- a/src/cpu/x86/vm/frame_x86.inline.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/x86/vm/frame_x86.inline.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -40,7 +40,7 @@
   _deopt_state = unknown;
 }
 
-inline frame::frame(intptr_t* sp, intptr_t* fp, address pc) {
+inline void frame::init(intptr_t* sp, intptr_t* fp, address pc) {
   _sp = sp;
   _unextended_sp = sp;
   _fp = fp;
@@ -58,6 +58,10 @@
   }
 }
 
+inline frame::frame(intptr_t* sp, intptr_t* fp, address pc) {
+  init(sp, fp, pc);
+}
+
 inline frame::frame(intptr_t* sp, intptr_t* unextended_sp, intptr_t* fp, address pc) {
   _sp = sp;
   _unextended_sp = unextended_sp;
--- a/src/cpu/x86/vm/vm_version_x86.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/x86/vm/vm_version_x86.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -570,10 +570,12 @@
   static uint cores_per_cpu()  {
     uint result = 1;
     if (is_intel()) {
-      if (supports_processor_topology()) {
+      bool supports_topology = supports_processor_topology();
+      if (supports_topology) {
         result = _cpuid_info.tpl_cpuidB1_ebx.bits.logical_cpus /
                  _cpuid_info.tpl_cpuidB0_ebx.bits.logical_cpus;
-      } else {
+      }
+      if (!supports_topology || result == 0) {
         result = (_cpuid_info.dcp_cpuid4_eax.bits.cores_per_cpu + 1);
       }
     } else if (is_amd()) {
--- a/src/cpu/zero/vm/frame_zero.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/cpu/zero/vm/frame_zero.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -441,3 +441,10 @@
   // unused... but returns fp() to minimize changes introduced by 7087445
   return fp();
 }
+
+#ifndef PRODUCT
+// This is a generic constructor which is only used by pns() in debug.cpp.
+frame::frame(void* sp, void* fp, void* pc) {
+  Unimplemented();
+}
+#endif
--- a/src/os_cpu/solaris_sparc/vm/os_solaris_sparc.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/os_cpu/solaris_sparc/vm/os_solaris_sparc.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -264,7 +264,7 @@
                 CAST_FROM_FN_PTR(address, os::current_frame));
   if (os::is_first_C_frame(&myframe)) {
     // stack is not walkable
-    return frame(NULL, NULL, NULL);
+    return frame(NULL, NULL, false);
   } else {
     return os::get_sender_for_C_frame(&myframe);
   }
--- a/src/share/vm/ci/ciTypeFlow.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/ci/ciTypeFlow.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -36,6 +36,7 @@
 #include "interpreter/bytecodes.hpp"
 #include "memory/allocation.inline.hpp"
 #include "opto/compile.hpp"
+#include "opto/node.hpp"
 #include "runtime/deoptimization.hpp"
 #include "utilities/growableArray.hpp"
 
--- a/src/share/vm/prims/unsafe.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/prims/unsafe.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -322,10 +322,33 @@
 UNSAFE_END
 
 #ifndef SUPPORTS_NATIVE_CX8
-// Keep old code for platforms which may not have atomic jlong (8 bytes) instructions
 
-// Volatile long versions must use locks if !VM_Version::supports_cx8().
-// support_cx8 is a surrogate for 'supports atomic long memory ops'.
+// VM_Version::supports_cx8() is a surrogate for 'supports atomic long memory ops'.
+//
+// On platforms which do not support atomic compare-and-swap of jlong (8 byte)
+// values we have to use a lock-based scheme to enforce atomicity. This has to be
+// applied to all Unsafe operations that set the value of a jlong field. Even so
+// the compareAndSwapLong operation will not be atomic with respect to direct stores
+// to the field from Java code. It is important therefore that any Java code that
+// utilizes these Unsafe jlong operations does not perform direct stores. To permit
+// direct loads of the field from Java code we must also use Atomic::store within the
+// locked regions. And for good measure, in case there are direct stores, we also
+// employ Atomic::load within those regions. Note that the field in question must be
+// volatile and so must have atomic load/store accesses applied at the Java level.
+//
+// The locking scheme could utilize a range of strategies for controlling the locking
+// granularity: from a lock per-field through to a single global lock. The latter is
+// the simplest and is used for the current implementation. Note that the Java object
+// that contains the field, can not, in general, be used for locking. To do so can lead
+// to deadlocks as we may introduce locking into what appears to the Java code to be a
+// lock-free path.
+//
+// As all the locked-regions are very short and themselves non-blocking we can treat
+// them as leaf routines and elide safepoint checks (ie we don't perform any thread
+// state transitions even when blocking for the lock). Note that if we do choose to
+// add safepoint checks and thread state transitions, we must ensure that we calculate
+// the address of the field _after_ we have acquired the lock, else the object may have
+// been moved by the GC
 
 UNSAFE_ENTRY(jlong, Unsafe_GetLongVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset))
   UnsafeWrapper("Unsafe_GetLongVolatile");
@@ -337,8 +360,8 @@
     else {
       Handle p (THREAD, JNIHandles::resolve(obj));
       jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
-      ObjectLocker ol(p, THREAD);
-      jlong value = *addr;
+      MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
+      jlong value = Atomic::load(addr);
       return value;
     }
   }
@@ -353,8 +376,8 @@
     else {
       Handle p (THREAD, JNIHandles::resolve(obj));
       jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
-      ObjectLocker ol(p, THREAD);
-      *addr = x;
+      MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
+      Atomic::store(x, addr);
     }
   }
 UNSAFE_END
@@ -463,8 +486,8 @@
     else {
       Handle p (THREAD, JNIHandles::resolve(obj));
       jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
-      ObjectLocker ol(p, THREAD);
-      *addr = x;
+      MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
+      Atomic::store(x, addr);
     }
   }
 #endif
@@ -1213,14 +1236,19 @@
   UnsafeWrapper("Unsafe_CompareAndSwapLong");
   Handle p (THREAD, JNIHandles::resolve(obj));
   jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
+#ifdef SUPPORTS_NATIVE_CX8
+  return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
+#else
   if (VM_Version::supports_cx8())
     return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
   else {
     jboolean success = false;
-    ObjectLocker ol(p, THREAD);
-    if (*addr == e) { *addr = x; success = true; }
+    MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
+    jlong val = Atomic::load(addr);
+    if (val == e) { Atomic::store(x, addr); success = true; }
     return success;
   }
+#endif
 UNSAFE_END
 
 UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time))
--- a/src/share/vm/runtime/frame.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/runtime/frame.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -91,6 +91,15 @@
   // Constructors
   frame();
 
+#ifndef PRODUCT
+  // This is a generic constructor which is only used by pns() in debug.cpp.
+  // pns (i.e. print native stack) uses this constructor to create a starting
+  // frame for stack walking. The implementation of this constructor is platform
+  // dependent (i.e. SPARC doesn't need an 'fp' argument an will ignore it) but
+  // we want to keep the signature generic because pns() is shared code.
+  frame(void* sp, void* fp, void* pc);
+#endif
+
   // Accessors
 
   // pc: Returns the pc at which this frame will continue normally.
--- a/src/share/vm/runtime/mutexLocker.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/runtime/mutexLocker.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -135,6 +135,10 @@
 Mutex*   JfrThreadGroups_lock         = NULL;
 #endif
 
+#ifndef SUPPORTS_NATIVE_CX8
+Mutex*   UnsafeJlong_lock             = NULL;
+#endif
+
 #define MAX_NUM_MUTEX 128
 static Monitor * _mutex_array[MAX_NUM_MUTEX];
 static int _num_mutex;
@@ -286,6 +290,9 @@
   def(JfrStacktrace_lock           , Mutex,   special,     true );
 #endif
 
+#ifndef SUPPORTS_NATIVE_CX8
+  def(UnsafeJlong_lock             , Mutex,   special,     false);
+#endif
 }
 
 GCMutexLocker::GCMutexLocker(Monitor * mutex) {
--- a/src/share/vm/runtime/mutexLocker.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/runtime/mutexLocker.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -151,6 +151,10 @@
 extern Mutex*   JfrThreadGroups_lock;            // protects JFR access to Thread Groups
 #endif
 
+#ifndef SUPPORTS_NATIVE_CX8
+extern Mutex*   UnsafeJlong_lock;                // provides Unsafe atomic updates to jlongs on platforms that don't support cx8
+#endif
+
 // A MutexLocker provides mutual exclusion with respect to a given mutex
 // for the scope which contains the locker.  The lock is an OS lock, not
 // an object lock, and the two do not interoperate.  Do not use Mutex-based
--- a/src/share/vm/utilities/debug.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/utilities/debug.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -666,6 +666,13 @@
   tty->print_cr("  pm(int pc)    - print Method* given compiled PC");
   tty->print_cr("  findm(intptr_t pc) - finds Method*");
   tty->print_cr("  find(intptr_t x)   - finds & prints nmethod/stub/bytecode/oop based on pointer into it");
+  tty->print_cr("  pns(void* sp, void* fp, void* pc)  - print native (i.e. mixed) stack trace. E.g.");
+  tty->print_cr("                   pns($sp, $rbp, $pc) on Linux/amd64 and Solaris/amd64 or");
+  tty->print_cr("                   pns($sp, $ebp, $pc) on Linux/x86 or");
+  tty->print_cr("                   pns($sp, 0, $pc)    on Linux/ppc64 or");
+  tty->print_cr("                   pns($sp + 0x7ff, 0, $pc) on Solaris/SPARC");
+  tty->print_cr("                 - in gdb do 'set overload-resolution off' before calling pns()");
+  tty->print_cr("                 - in dbx do 'frame 1' before calling pns()");
 
   tty->print_cr("misc.");
   tty->print_cr("  flush()       - flushes the log file");
@@ -678,3 +685,56 @@
 }
 
 #endif // !PRODUCT
+
+void print_native_stack(outputStream* st, frame fr, Thread* t, char* buf, int buf_size) {
+
+  // see if it's a valid frame
+  if (fr.pc()) {
+    st->print_cr("Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)");
+
+    int count = 0;
+    while (count++ < StackPrintLimit) {
+      fr.print_on_error(st, buf, buf_size);
+      st->cr();
+      // Compiled code may use EBP register on x86 so it looks like
+      // non-walkable C frame. Use frame.sender() for java frames.
+      if (t && t->is_Java_thread()) {
+        // Catch very first native frame by using stack address.
+        // For JavaThread stack_base and stack_size should be set.
+        if (!t->on_local_stack((address)(fr.real_fp() + 1))) {
+          break;
+        }
+        if (fr.is_java_frame() || fr.is_native_frame() || fr.is_runtime_frame()) {
+          RegisterMap map((JavaThread*)t, false); // No update
+          fr = fr.sender(&map);
+        } else {
+          fr = os::get_sender_for_C_frame(&fr);
+        }
+      } else {
+        // is_first_C_frame() does only simple checks for frame pointer,
+        // it will pass if java compiled code has a pointer in EBP.
+        if (os::is_first_C_frame(&fr)) break;
+        fr = os::get_sender_for_C_frame(&fr);
+      }
+    }
+
+    if (count > StackPrintLimit) {
+      st->print_cr("...<more frames>...");
+    }
+
+    st->cr();
+  }
+}
+
+#ifndef PRODUCT
+
+extern "C" void pns(void* sp, void* fp, void* pc) { // print native stack
+  Command c("pns");
+  static char buf[O_BUFLEN];
+  Thread* t = ThreadLocalStorage::get_thread_slow();
+  // Call generic frame constructor (certain arguments may be ignored)
+  frame fr(sp, fp, pc);
+  print_native_stack(tty, fr, t, buf, sizeof(buf));
+}
+
+#endif // !PRODUCT
--- a/src/share/vm/utilities/debug.hpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/utilities/debug.hpp	Wed Jan 21 17:07:26 2015 +0000
@@ -265,4 +265,7 @@
 void pd_ps(frame f);
 void pd_obfuscate_location(char *buf, size_t buflen);
 
+class outputStream;
+void print_native_stack(outputStream* st, frame fr, Thread* t, char* buf, int buf_size);
+
 #endif // SHARE_VM_UTILITIES_DEBUG_HPP
--- a/src/share/vm/utilities/vmError.cpp	Tue Jan 20 13:47:31 2015 -0800
+++ b/src/share/vm/utilities/vmError.cpp	Wed Jan 21 17:07:26 2015 +0000
@@ -576,7 +576,7 @@
 
   STEP(120, "(printing native stack)" )
 
-     if (_verbose) {
+   if (_verbose) {
      if (os::platform_print_native_stack(st, _context, buf, sizeof(buf))) {
        // We have printed the native stack in platform-specific code
        // Windows/x64 needs special handling.
@@ -584,43 +584,7 @@
        frame fr = _context ? os::fetch_frame_from_context(_context)
                            : os::current_frame();
 
-       // see if it's a valid frame
-       if (fr.pc()) {
-          st->print_cr("Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)");
-
-
-          int count = 0;
-          while (count++ < StackPrintLimit) {
-             fr.print_on_error(st, buf, sizeof(buf));
-             st->cr();
-             // Compiled code may use EBP register on x86 so it looks like
-             // non-walkable C frame. Use frame.sender() for java frames.
-             if (_thread && _thread->is_Java_thread()) {
-               // Catch very first native frame by using stack address.
-               // For JavaThread stack_base and stack_size should be set.
-               if (!_thread->on_local_stack((address)(fr.sender_sp() + 1))) {
-                 break;
-               }
-               if (fr.is_java_frame()) {
-                 RegisterMap map((JavaThread*)_thread, false); // No update
-                 fr = fr.sender(&map);
-               } else {
-                 fr = os::get_sender_for_C_frame(&fr);
-               }
-             } else {
-               // is_first_C_frame() does only simple checks for frame pointer,
-               // it will pass if java compiled code has a pointer in EBP.
-               if (os::is_first_C_frame(&fr)) break;
-               fr = os::get_sender_for_C_frame(&fr);
-             }
-          }
-
-          if (count > StackPrintLimit) {
-             st->print_cr("...<more frames>...");
-          }
-
-          st->cr();
-       }
+       print_native_stack(st, fr, _thread, buf, sizeof(buf));
      }
    }
 
--- a/test/serviceability/sa/jmap-hashcode/Test8028623.java	Tue Jan 20 13:47:31 2015 -0800
+++ b/test/serviceability/sa/jmap-hashcode/Test8028623.java	Wed Jan 21 17:07:26 2015 +0000
@@ -33,20 +33,25 @@
 
 import com.oracle.java.testlibrary.JDKToolLauncher;
 import com.oracle.java.testlibrary.OutputBuffer;
+import com.oracle.java.testlibrary.Platform;
 import com.oracle.java.testlibrary.ProcessTools;
 
 import java.io.File;
 
 public class Test8028623 {
 
-  public static int à = 1;
+  public static int \u00CB = 1;
   public static String dumpFile = "heap.out";
 
   public static void main (String[] args) {
 
-    System.out.println(Ã);
+    System.out.println(\u00CB);
 
     try {
+        if (!Platform.shouldSAAttach()) {
+            System.out.println("SA attach not expected to work - test skipped.");
+            return;
+        }
         int pid = ProcessTools.getProcessId();
         JDKToolLauncher jmap = JDKToolLauncher.create("jmap")
                                               .addToolArg("-F")
--- a/test/testlibrary/com/oracle/java/testlibrary/Platform.java	Tue Jan 20 13:47:31 2015 -0800
+++ b/test/testlibrary/com/oracle/java/testlibrary/Platform.java	Wed Jan 21 17:07:26 2015 +0000
@@ -23,12 +23,15 @@
 
 package com.oracle.java.testlibrary;
 
+import com.oracle.java.testlibrary.Utils;
+
 public class Platform {
     private static final String osName      = System.getProperty("os.name");
     private static final String dataModel   = System.getProperty("sun.arch.data.model");
     private static final String vmVersion   = System.getProperty("java.vm.version");
     private static final String osArch      = System.getProperty("os.arch");
     private static final String vmName      = System.getProperty("java.vm.name");
+    private static final String userName    = System.getProperty("user.name");
 
     public static boolean isClient() {
         return vmName.endsWith(" Client VM");
@@ -121,4 +124,56 @@
         return osArch;
     }
 
+    /**
+     * Return a boolean for whether we expect to be able to attach
+     * the SA to our own processes on this system.
+     */
+    public static boolean shouldSAAttach() throws Exception {
+
+        if (isLinux()) {
+            return canPtraceAttachLinux();
+        } else if (isOSX()) {
+            return canAttachOSX();
+        } else {
+            // Other platforms expected to work:
+            return true;
+        }
+    }
+
+    /**
+     * On Linux, first check the SELinux boolean "deny_ptrace" and return false
+     * as we expect to be denied if that is "1".  Then expect permission to attach
+     * if we are root, so return true.  Then return false for an expected denial
+     * if "ptrace_scope" is 1, and true otherwise.
+     */
+    public static boolean canPtraceAttachLinux() throws Exception {
+
+        // SELinux deny_ptrace:
+        String deny_ptrace = Utils.fileAsString("/sys/fs/selinux/booleans/deny_ptrace");
+        if (deny_ptrace != null && deny_ptrace.contains("1")) {
+            // ptrace will be denied:
+            return false;
+        }
+
+        if (userName.equals("root")) {
+            return true;
+        }
+
+        // ptrace_scope:
+        String ptrace_scope = Utils.fileAsString("/proc/sys/kernel/yama/ptrace_scope");
+        if (ptrace_scope != null && ptrace_scope.contains("1")) {
+            // ptrace will be denied:
+            return false;
+        }
+
+        // Otherwise expect to be permitted:
+        return true;
+    }
+
+    /**
+     * On OSX, expect permission to attach only if we are root.
+     */
+    public static boolean canAttachOSX() throws Exception {
+        return userName.equals("root");
+    }
 }
--- a/test/testlibrary/com/oracle/java/testlibrary/Utils.java	Tue Jan 20 13:47:31 2015 -0800
+++ b/test/testlibrary/com/oracle/java/testlibrary/Utils.java	Wed Jan 21 17:07:26 2015 +0000
@@ -299,6 +299,35 @@
     }
 
     /**
+     * Return the contents of the named file as a single String,
+     * or null if not found.
+     * @param filename name of the file to read
+     * @return String contents of file, or null if file not found.
+     */
+    public static String fileAsString(String filename) {
+        StringBuilder result = new StringBuilder();
+        try {
+            File file = new File(filename);
+            if (file.exists()) {
+                BufferedReader reader = new BufferedReader(new FileReader(file));
+                while (true) {
+                    String line = reader.readLine();
+                    if (line == null) {
+                        break;
+                    }
+                    result.append(line).append("\n");
+                }
+            } else {
+                // Does not exist:
+                return null;
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        return result.toString();
+    }
+
+    /**
      * @return Unsafe instance.
      */
     public static synchronized Unsafe getUnsafe() {