6953058: G1: A bigapp crashes with SIGSEGV in compiled code
Summary: In C2's G1 post write barrier, the loads of the buffer and index fields from the DirtyCardQueue structure may be moved across a safepoint. Use the current value of "control" in the C2 IR to limit how far these loads can move.
Reviewed-by: never, iveresov, kvn
--- a/hotspot/src/share/vm/opto/graphKit.cpp Thu May 27 13:09:56 2010 -0700
+++ b/hotspot/src/share/vm/opto/graphKit.cpp Mon Jun 07 17:46:04 2010 -0700
@@ -3487,7 +3487,6 @@
Node* tls = __ thread(); // ThreadLocalStorage
- Node* no_ctrl = NULL;
Node* no_base = __ top();
float likely = PROB_LIKELY(0.999);
float unlikely = PROB_UNLIKELY(0.999);
@@ -3511,10 +3510,10 @@
Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset));
// Now some values
-
- Node* index = __ load(no_ctrl, index_adr, TypeInt::INT, T_INT, Compile::AliasIdxRaw);
- Node* buffer = __ load(no_ctrl, buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw);
-
+ // Use ctrl to avoid hoisting these values past a safepoint, which could
+ // potentially reset these fields in the JavaThread.
+ Node* index = __ load(__ ctrl(), index_adr, TypeInt::INT, T_INT, Compile::AliasIdxRaw);
+ Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw);
// Convert the store obj pointer to an int prior to doing math on it
// Must use ctrl to prevent "integerized oop" existing across safepoint