Hi Dan,
On 21/07/2020 3:07 am, Daniel D. Daugherty wrote:
On 7/20/20 1:53 AM, David Holmes wrote:
Hi Kim,
Thanks for looking at this.
Updated webrev at:
http://cr.openjdk.java.net/~dholmes/8249650/webrev.v2/
I like this cleanup very much!
Thanks for looking at it.
src/hotspot/share/classfile/javaClasses.cpp
No comments.
src/hotspot/share/classfile/verifier.cpp
L298: JavaThread* thread = (JavaThread*)THREAD;
L307: ResourceMark rm(THREAD);
Since we've gone to the trouble of creating the 'thread' variable,
I would prefer it to be used instead of THREAD where possible.
Okay I made this change as we already use "thread" throughout that method.
src/hotspot/share/jvmci/jvmciCompilerToVM.cpp
L1021: HandleMark hm;
Can this be 'hm(THREAD)'? (Not your problem, but while you're
in that file?)
It probably could but there are around 8 such uses and I don't want to
expand this change any further than necessary for the current issue. I
filed a general RFE for things that should take advantage of having a
current thread reference already (that will encompass Coleen's
make_local(obj) change as well).
https://bugs.openjdk.java.net/browse/JDK-8249837
src/hotspot/share/prims/jni.cpp
No comments.
src/hotspot/share/prims/jvm.cpp
L140: ResourceMark rm;
Can this be 'rm(THREAD)'? (Not your problem, but while you're
in that file?)
L611: Handle stackStream_h(THREAD,
JNIHandles::resolve_non_null(stackStream));
L617: objArrayHandle frames_array_h(THREAD, fa);
L626: return JNIHandles::make_local(THREAD, result);
Since we've gone to the trouble of creating the 'jt' variable,
I would prefer it to be used instead of THREAD where possible.
L767: vframeStream vfst(thread);
L788 return (jclass) JNIHandles::make_local(THREAD,
m->method_holder()->java_mirror());
Can we use 'thread' on L788? (preferred)
Can we use 'THREAD' on L767? (less preferred)
L949: ResourceMark rm(THREAD);
L951: Handle class_loader (THREAD, JNIHandles::resolve(loader));
L955: THREAD);
L957: Handle protection_domain (THREAD, JNIHandles::resolve(pd));
L968: return (jclass) JNIHandles::make_local(THREAD,
k->java_mirror());
Since we've gone to the trouble of creating the 'jt' variable,
I would prefer it to be used instead of THREAD where possible.
As per our slack chat, and the fact you are okay with things as-is, I
will forego a more general "consistency" pass as it is unclear what is
best here. As Coleen notes THREAD is generally understood to always be
the current thread, while thread/jthread/jt could be any old thread in
general. Also THREAD usage can highlight a Thread* API, while "thread"
has to be used for JavaThread* API - but obviously that needs to be
carefully and consistently applied to be useful. :)
L986: JavaThread* jt = (JavaThread*) THREAD;
This 'jt' is unused and can be deleted (Not your problem, but
while you're
in that file?)
Fixed (and another case elsewhere).
L1154: while (*p != '\0') {
L1155: if (*p == '.') {
L1156: *p = '/';
L1157: }
L1158: p++;
Nit - the indents are wrong on L1155-58. (Not your problem, but
while you're
in that file?)
Fixed
L1389: ResourceMark rm(THREAD);
L1446: return JNIHandles::make_local(THREAD, result);
L1460: return JNIHandles::make_local(THREAD, result);
Can we use 'thread' on L1389? (preferred) And then the line you
touched could also be 'thread' and we'll be consistent in this
function...
Left as-is.
L3287: oop jthread = thread->threadObj();
L3288: assert (thread != NULL, "no current thread!");
I think the assert is wrong. It should be:
assert(jthread != NULL, "no current thread!");
If 'thread == NULL', then we would have crashed at L3287.
Also notice that I deleted the extra ' ' before '('. (Not
your problem, but while you're in that file?)
Fixed. I was initially concerned about bootstrapping but it is fine - we
ensure we set threadObj() before executing any Java code.
L3289: return JNIHandles::make_local(THREAD, jthread);
Can you use 'thread' instead of 'THREAD' here for consistency?
L3681: method_handle = Handle(THREAD,
JNIHandles::resolve(method));
L3682: Handle receiver(THREAD, JNIHandles::resolve(obj));
L3683: objArrayHandle args(THREAD,
objArrayOop(JNIHandles::resolve(args0)));
L3685: jobject res = JNIHandles::make_local(THREAD, result);
Can you use 'thread' instead of 'THREAD' here for consistency?
L3705: objArrayHandle args(THREAD,
objArrayOop(JNIHandles::resolve(args0)));
L3707 jobject res = JNIHandles::make_local(THREAD, result);
Can you use 'thread' instead of 'THREAD' here for consistency?
Left as-is.
src/hotspot/share/prims/methodHandles.cpp
No comments.
src/hotspot/share/prims/methodHandles.hpp
No comments.
src/hotspot/share/prims/unsafe.cpp
No comments.
src/hotspot/share/prims/whitebox.cpp
No comments.
src/hotspot/share/runtime/jniHandles.cpp
No comments.
src/hotspot/share/runtime/jniHandles.hpp
No comments.
src/hotspot/share/services/management.cpp
No comments.
None of my comments above are "must do". If you choose to make the
changes, a new webrev isn't required, but would be useful for a
sanity check.
In addition to the tweak above I found a bunch of make_locasl(obj)
usages in jvm.cpp and jni.cpp thanks to Coleen, which I have also fixed.
Updated webrev:
http://cr.openjdk.java.net/~dholmes/8249650/webrev.v3/
If this passes tier 1-3 re-testing then I plan to push.
Thanks,
David
-----
Thumbs up.
Dan
On 20/07/2020 3:22 pm, Kim Barrett wrote:
On Jul 20, 2020, at 12:16 AM, David Holmes <david.hol...@oracle.com>
wrote:
Subject line got truncated by accident ...
On 20/07/2020 11:06 am, David Holmes wrote:
Bug: https://bugs.openjdk.java.net/browse/JDK-8249650
webrev: http://cr.openjdk.java.net/~dholmes/8249650/webrev/
This is a simple cleanup that touches files across a number of VM
areas - hence the cross-post.
Whilst working on a different JNI fix I noticed that in most cases
in jni.cpp we were using the following form of make_local:
JNIHandles::make_local(env, obj);
and what that form does is first extract the thread from the JNIEnv:
JavaThread* thread = JavaThread::thread_from_jni_environment(env);
return thread->active_handles()->allocate_handle(obj);
but there is also another, faster, variant for when you already
have the "thread":
jobject JNIHandles::make_local(Thread* thread, oop obj) {
return thread->active_handles()->allocate_handle(obj);
}
When you look at the JNI_ENTRY wrapper (and related JVM_ENTRY,
WB_ENTRY, UNSAFE_ENTRY etc) it has already extracted the thread
from the JNIEnv:
JavaThread* thread=JavaThread::thread_from_jni_environment(env);
and further defined:
Thread* THREAD = thread;
so we always already have direct access to the "thread" available
(or indirect via TRAPS), and in fact we can end up removing the
make_local(JNIEnv* env, oop obj) variant altogether.
Along the way I spotted some related issues with unnecessary use of
Thread::current() when it is already available from TRAPS, and some
other cases where we extracted the JNIEnv from a thread only to
later extract the thread from the JNIEnv.
Testing: tiers 1 - 3
Thanks,
David
-----
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src/hotspot/share/classfile/javaClasses.cpp
439 JNIEnv *env = thread->jni_environment();
Since env is no longer used on the next line, move this down to where
it is used, at line 444.
Fixed.
------------------------------------------------------------------------------
src/hotspot/share/classfile/verifier.cpp
299 JNIEnv *env = thread->jni_environment();
env now seems to only be used at line 320. Move this closer.
Fixed.
------------------------------------------------------------------------------
src/hotspot/share/prims/jni.cpp
743 result = JNIHandles::make_local(THREAD, result_handle());
jni_PopLocalFrame is now using a mix of "thread" and "THREAD", where
previously it just used "thread". Maybe this change shouldn't be made?
Or can the other uses be changed to THREAD for consistency?
"thread" and "THREAD" are interchangeable for anything expecting a
"Thread*" (and somewhat surprisingly a number of API's that only work
for JavaThreads actually take a Thread*. :( ). I had choice between
trying to be file-wide consistent with the make_local calls, versus
local-code consistent, and used THREAD as it is available in both
JNI_ENTRY and via TRAPS. But I can certainly make a local change to
"thread" for local consistency.
------------------------------------------------------------------------------
src/hotspot/share/prims/jvm.cpp
The calls to JvmtiExport::post_vm_object_alloc have to use "thread"
instead of "THREAD", even though other places nearby are using
"THREAD". That inconsistency is kind of unfortunate, but doesn't seem
easily avoidable.
Everything that uses THREAD in a JVM_ENTRY method can be changed to
use "thread" instead. But I'm not sure it's a consistency worth
pursuing at least as part of these changes (there are likely similar
issues with most of the touched files).
Thanks,
David
------------------------------------------------------------------------------
