RFR(XXS): 8227338: templateInterpreter.cpp: copy_table() needs to be safer

[Daniel D. Daugherty]

Greetings,

I've made one minor tweak based on Kim's code review.

Here's the full webrev:

http://cr.openjdk.java.net/~dcubed/8227338-webrev/1_for_jdk14.full/

Here's the incremental webrev:

http://cr.openjdk.java.net/~dcubed/8227338-webrev/1_for_jdk14.inc/

Here's the context diff:

$ hg diff
diff -r 32fe92d8b539 src/hotspot/share/interpreter/templateInterpreter.cpp
--- a/src/hotspot/share/interpreter/templateInterpreter.cpp    Mon Jul 
08 16:58:27 2019 -0400
+++ b/src/hotspot/share/interpreter/templateInterpreter.cpp    Tue Jul 
09 10:02:46 2019 -0400
@@ -283,7 +283,7 @@
    // Copy non-overlapping tables.
    if (SafepointSynchronize::is_at_safepoint()) {
      // Nothing is using the table at a safepoint so skip atomic word copy.
-    while (size-- > 0) *to++ = *from++;
+    Copy::disjoint_words((HeapWord*)from, (HeapWord*)to, (size_t)size);
    } else {
      // Use atomic word copy when not at a safepoint for safety.
      Copy::disjoint_words_atomic((HeapWord*)from, (HeapWord*)to, 
(size_t)size);

Thanks, in advance, for questions, comments or suggestions.

Dan


On 7/6/19 9:53 AM, Daniel D. Daugherty wrote:
> Greetings,
>
> During the code review for the following fix:
>
>     JDK-8227117 normal interpreter table is not restored after single 
> stepping with TLH
>     https://bugs.openjdk.java.net/browse/JDK-8227117
>
> Erik O. noticed a potential race with templateInterpreter.cpp: 
> copy_table()
> depending on C++ compiler optimizations. The following bug is being used
> to fix this issue:
>
>     JDK-8227338 templateInterpreter.cpp: copy_table() needs to be safer
>     https://bugs.openjdk.java.net/browse/JDK-8227338
>
> Here's the webrev URL:
>
>     http://cr.openjdk.java.net/~dcubed/8227338-webrev/0_for_jdk14/
>
> This fix has been tested via Mach5 Tier[1-3] on Oracle's usual platforms.
> Mach5 tier[4-6] is running now. It has also been tested with the manual
> jdb test from JDK-8227117 using 'release' and 'fastdebug' bits.
>
> Thanks, in advance, for questions, comments or suggestions.
>
> Dan
>