Hi,
Testing found a bug in the original webrev. Namely, when clearing out a pending
exception and returning null in the JVMCI ..._or_null stubs, the
JavaThread::_vm_result field was not being set to NULL. I've addressed this in
v2 of the webrev:
Relative diff for bug fix:
-----------------------------------------------------------------------------------------------
-// Manages a scope in which a failed heap allocation will throw an exception.
-// The pending exception is cleared when leaving the scope.
+// Manages a scope for a JVMCI runtime call that attempts a heap allocation.
+// If there is a pending exception upon closing the scope and the runtime
+// call is of the variety where allocation failure returns NULL without an
+// exception, the following action is taken:
+// 1. The pending exception is cleared
+// 2. NULL is written to JavaThread::_vm_result
+// 3. Checks that an OutOfMemoryError is
Universe::out_of_memory_error_retry().
class RetryableAllocationMark: public StackObj {
private:
JavaThread* _thread;
public:
RetryableAllocationMark(JavaThread* thread, bool activate) {
if (activate) {
- assert(thread->in_retryable_allocation(), "retryable allocation scope is
non-reentrant");
+ assert(!thread->in_retryable_allocation(), "retryable allocation scope is
non-reentrant");
_thread = thread;
_thread->set_in_retryable_allocation(true);
} else {
@@ -136,6 +141,7 @@
ResourceMark rm;
fatal("Unexpected exception in scope of retryable allocation: " INTPTR_FORMAT
" of type %s", p2i(ex), ex->klass()->external_name());
}
+ _thread->set_vm_result(NULL);
}
}
}
-----------------------------------------------------------------------------------------------
I also took the opportunity to factor out negative array length checking:
-----------------------------------------------------------------------------------------------
diff -r 4d36f5998a8b src/hotspot/share/oops/arrayKlass.cpp
--- a/src/hotspot/share/oops/arrayKlass.cpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/arrayKlass.cpp Fri Oct 05 17:17:17 2018 +0200
@@ -130,9 +130,6 @@
}
objArrayOop ArrayKlass::allocate_arrayArray(int n, int length, TRAPS) {
- if (length < 0) {
- THROW_MSG_0(vmSymbols::java_lang_NegativeArraySizeException(),
err_msg("%d", length));
- }
check_array_allocation_length(length,
arrayOopDesc::max_array_length(T_ARRAY), CHECK_0);
int size = objArrayOopDesc::object_size(length);
Klass* k = array_klass(n+dimension(), CHECK_0);
diff -r 4d36f5998a8b src/hotspot/share/oops/instanceKlass.cpp
--- a/src/hotspot/share/oops/instanceKlass.cpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/instanceKlass.cpp Fri Oct 05 17:17:17 2018 +0200
@@ -1201,9 +1201,6 @@
}
objArrayOop InstanceKlass::allocate_objArray(int n, int length, TRAPS) {
- if (length < 0) {
- THROW_MSG_0(vmSymbols::java_lang_NegativeArraySizeException(),
err_msg("%d", length));
- }
check_array_allocation_length(length,
arrayOopDesc::max_array_length(T_OBJECT), CHECK_NULL);
int size = objArrayOopDesc::object_size(length);
Klass* ak = array_klass(n, CHECK_NULL);
diff -r 4d36f5998a8b src/hotspot/share/oops/klass.cpp
--- a/src/hotspot/share/oops/klass.cpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/klass.cpp Fri Oct 05 17:17:17 2018 +0200
@@ -620,6 +620,8 @@
} else {
THROW_OOP(Universe::out_of_memory_error_retry());
}
+ } else if (length < 0) {
+ THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d",
length));
}
}
diff -r 4d36f5998a8b src/hotspot/share/oops/klass.hpp
--- a/src/hotspot/share/oops/klass.hpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/klass.hpp Fri Oct 05 17:17:17 2018 +0200
@@ -514,7 +514,7 @@
virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
virtual Klass* array_klass_impl(bool or_null, TRAPS);
- // Error handling when length > max_length
+ // Error handling when length > max_length or length < 0
static void check_array_allocation_length(int length, int max_length,
TRAPS);
void set_vtable_length(int len) { _vtable_len= len; }
diff -r 4d36f5998a8b src/hotspot/share/oops/objArrayKlass.cpp
--- a/src/hotspot/share/oops/objArrayKlass.cpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/objArrayKlass.cpp Fri Oct 05 17:17:17 2018 +0200
@@ -170,14 +170,10 @@
}
objArrayOop ObjArrayKlass::allocate(int length, TRAPS) {
- if (length >= 0) {
- check_array_allocation_length(length,
arrayOopDesc::max_array_length(T_OBJECT), CHECK_0);
- int size = objArrayOopDesc::object_size(length);
- return (objArrayOop)Universe::heap()->array_allocate(this, size, length,
- /* do_zero */ true,
THREAD);
- } else {
- THROW_MSG_0(vmSymbols::java_lang_NegativeArraySizeException(),
err_msg("%d", length));
- }
+ check_array_allocation_length(length,
arrayOopDesc::max_array_length(T_OBJECT), CHECK_0);
+ int size = objArrayOopDesc::object_size(length);
+ return (objArrayOop)Universe::heap()->array_allocate(this, size, length,
+ /* do_zero */ true,
THREAD);
}
static int multi_alloc_counter = 0;
diff -r 4d36f5998a8b src/hotspot/share/oops/typeArrayKlass.cpp
--- a/src/hotspot/share/oops/typeArrayKlass.cpp Fri Oct 05 17:04:06 2018 +0200
+++ b/src/hotspot/share/oops/typeArrayKlass.cpp Fri Oct 05 17:17:17 2018 +0200
@@ -99,14 +99,10 @@
typeArrayOop TypeArrayKlass::allocate_common(int length, bool do_zero, TRAPS) {
assert(log2_element_size() >= 0, "bad scale");
- if (length >= 0) {
- check_array_allocation_length(length, max_length(), CHECK_NULL);
- size_t size = typeArrayOopDesc::object_size(layout_helper(), length);
- return (typeArrayOop)Universe::heap()->array_allocate(this, (int)size,
length,
- do_zero, CHECK_NULL);
- } else {
- THROW_MSG_0(vmSymbols::java_lang_NegativeArraySizeException(),
err_msg("%d", length));
- }
+ check_array_allocation_length(length, max_length(), CHECK_NULL);
+ size_t size = typeArrayOopDesc::object_size(layout_helper(), length);
+ return (typeArrayOop)Universe::heap()->array_allocate(this, (int)size,
length,
+ do_zero, CHECK_NULL);
}
oop TypeArrayKlass::multi_allocate(int rank, jint* last_size, TRAPS) {
-----------------------------------------------------------------------------------------------
Please confirm review these new changes:
http://cr.openjdk.java.net/~dnsimon/8208686v2
-Doug
On 4 Oct 2018, at 00:20, Doug Simon <doug.si...@oracle.com> wrote:
Thanks for the reviews Serguei and Vladimir.
Unless I hear objections in the next 24 hours, I'll push this webrev.
-Doug
On 3 Oct 2018, at 03:14, serguei.spit...@oracle.com wrote:
Hi Doug,
The JVMTI related part looks good to me.
Thank you for fixing it!
Thanks,
Serguei
On 10/2/18 1:11 AM, Doug Simon wrote:
It would be great to get some input from the non-compilers teams on this RFR.
-Doug
On 28 Sep 2018, at 19:51, Vladimir Kozlov <vladimir.koz...@oracle.com> wrote:
To let you know, me and Tom R. did review these changes and agreed that it is
the least intrusive changes for Hotspot shared code.
Thanks,
Vladimir
On 9/25/18 8:11 AM, Daniel D. Daugherty wrote:
Adding serviceability-dev@... since this is JVM/TI...
Dan
On 9/25/18 10:48 AM, Doug Simon wrote:
A major design point of Graal is to treat allocations as non-side effecting to
give more freedom to the optimizer by reducing the number of distinct
FrameStates that need to be managed. When failing an allocation, Graal will
deoptimize to the last side effecting instruction before the allocation. This
mean the VM code for heap allocation will potentially be executed twice, once
from Graal compiled code and then again in the interpreter. While this is
perfectly fine according to the JVM specification, it can cause confusing
behavior for JVMTI based tools. They will receive 2 ResourceExhausted events
for a single allocation. Furthermore, the first ResourceExhausted event (on the
Graal allocation slow path) might denote a bytecode instruction that performs
no allocation, making it hard to debug the memory failure.
The proposed solution is to add an extra set of JVMCI VM runtime calls for
allocation. These entry points will attempt the allocation and upon failure,
skip side-effects such as posting JVMTI events or handling
-XX:OnOutOfMemoryError. The compiled code using these entry points is expected
deoptmize on null.
The path from these new entry points to where allocation can fail goes through
quite a bit of VM code. One could modify all these paths by:
* Returning null instead of throwing an exception on failure.
* Adding a `bool null_on_fail` argument to all relevant methods.
* Adding extra null checking where necessary after each call to these methods
when `null_on_fail == true`.
This represents a significant number of changes.
Instead, the proposed solution introduces a new _in_retryable_allocation
thread-local. This way, only the entry points and allocation routines that
raise an exception need to be modified. Failure is communicated back to the new
entry points by throwing a special pre-allocated OOME object (i.e.,
Universe::out_of_memory_error_retry()) which must not propagate back to Java
code. Use of this object is not strictly necessary; it is introduced to
highlight/document the special allocation mode.
The proposed solution is at http://cr.openjdk.java.net/~dnsimon/8208686.
THE JBS bug is: https://bugs.openjdk.java.net/browse/JDK-8208686
-Doug
