#else // !DEBUG
#undef NEXT_INSN
#define NEXT_INSN goto *((pc++)->insn)
-#define REWRITE_INSN(INSN,SLOT,VALUE) \
- do { \
- pc[-2].insn = INSN; \
- pc[-1].SLOT = VALUE; \
- } \
- while (0)
+
+// REWRITE_INSN does nothing.
+//
+// Rewriting a multi-word instruction in the presence of multiple
+// threads leads to a data race if a thread reads part of an
+// instruction while some other thread is rewriting that instruction.
+// For example, an invokespecial instruction may be rewritten to
+// invokespecial_resolved and its operand changed from an index to a
+// pointer while another thread is executing invokespecial. This
+// other thread then reads the pointer that is now the operand of
+// invokespecial_resolved and tries to use it as an index.
+//
+// Fixing this requires either spinlocks, a more elaborate data
+// structure, or even per-thread allocated pages. It's clear from the
+// locking in meth->compile below that the presence of multiple
+// threads was contemplated when this code was written, but the full
+// consequences were not fully appreciated.
+#define REWRITE_INSN(INSN,SLOT,VALUE)
#undef INTERP_REPORT_EXCEPTION
#define INTERP_REPORT_EXCEPTION(Jthrowable) /* not needed when not debugging */
{
/* here goes the magic again... */
ffi_cif *cif = &rmeth->cif;
- ffi_raw *raw = (ffi_raw*) sp;
+ INTERP_FFI_RAW_TYPE *raw = (INTERP_FFI_RAW_TYPE *) sp;
_Jv_value rvalue;
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