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-rw-r--r--erts/emulator/beam/beam_emu.c1
-rw-r--r--erts/emulator/beam/erl_message.h16
-rw-r--r--erts/emulator/beam/msg_instrs.tab21
-rw-r--r--erts/emulator/beam/ops.tab7
4 files changed, 26 insertions, 19 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index bc95ccec52..ef9abcde08 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -1454,6 +1454,7 @@ handle_error(Process* c_p, BeamInstr* pc, Eterm* reg, ErtsCodeMFA *bif_mfa)
reg[3] = c_p->ftrace;
if ((new_pc = next_catch(c_p, reg))) {
c_p->cp = 0; /* To avoid keeping stale references. */
+ c_p->msg.saved_last = 0; /* No longer safe to use this position */
return new_pc;
}
if (c_p->catches > 0) erts_exit(ERTS_ERROR_EXIT, "Catch not found");
diff --git a/erts/emulator/beam/erl_message.h b/erts/emulator/beam/erl_message.h
index 9c8cf84e43..a14f4f51d8 100644
--- a/erts/emulator/beam/erl_message.h
+++ b/erts/emulator/beam/erl_message.h
@@ -167,10 +167,9 @@ typedef struct {
Sint len; /* queue length */
/*
- * The following two fields are used by the recv_mark/1 and
+ * The following field is used by the recv_mark/1 and
* recv_set/1 instructions.
*/
- BeamInstr* mark; /* address to rec_loop/2 instruction */
ErtsMessage** saved_last; /* saved last pointer */
} ErlMessageQueue;
@@ -236,12 +235,17 @@ typedef struct erl_trace_message_queue__ {
(p)->msg.len--; \
if (__mp == NULL) \
(p)->msg.last = (p)->msg.save; \
- (p)->msg.mark = 0; \
} while(0)
-/* Reset message save point (after receive match) */
-#define JOIN_MESSAGE(p) \
- (p)->msg.save = &(p)->msg.first
+/*
+ * Reset message save point (after receive match).
+ * Also invalidate the saved position since it may no
+ * longer be safe to use.
+ */
+#define JOIN_MESSAGE(p) do { \
+ (p)->msg.save = &(p)->msg.first; \
+ (p)->msg.saved_last = 0; \
+} while(0)
/* Save current message */
#define SAVE_MESSAGE(p) \
diff --git a/erts/emulator/beam/msg_instrs.tab b/erts/emulator/beam/msg_instrs.tab
index 8055a8616f..d6d4d2fb49 100644
--- a/erts/emulator/beam/msg_instrs.tab
+++ b/erts/emulator/beam/msg_instrs.tab
@@ -43,27 +43,23 @@
// *
// */
-recv_mark(Dest) {
+i_recv_mark() {
/*
- * Save the current position in message buffer and the
- * the label for the loop_rec/2 instruction for the
- * the receive statement.
+ * Save the current position in message buffer.
*/
- $SET_REL_I(c_p->msg.mark, $Dest);
c_p->msg.saved_last = c_p->msg.last;
}
i_recv_set() {
/*
- * If the mark is valid (points to the loop_rec/2
- * instruction that follows), we know that the saved
- * position points to the first message that could
- * possibly be matched out.
+ * If c_p->msg.saved_last is non-zero, it points to the first
+ * message that could possibly be matched out.
*
- * If the mark is invalid, we do nothing, meaning that
- * we will look through all messages in the message queue.
+ * If c_p->msg.saved_last is zero, it means that it was invalidated
+ * because another receive was executed before this i_recv_set()
+ * instruction was reached.
*/
- if (c_p->msg.mark == (BeamInstr *) ($NEXT_INSTRUCTION)) {
+ if (c_p->msg.saved_last) {
c_p->msg.save = c_p->msg.saved_last;
}
SET_I($NEXT_INSTRUCTION);
@@ -131,6 +127,7 @@ i_loop_rec(Dest) {
ASSERT(HTOP == c_p->htop && E == c_p->stop);
/* TODO: Add DTrace probe for this bad message situation? */
UNLINK_MESSAGE(c_p, msgp);
+ c_p->msg.saved_last = 0; /* Better safe than sorry. */
msgp->next = NULL;
erts_cleanup_messages(msgp);
goto loop_rec__;
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index a560bde920..3df91056cb 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1565,7 +1565,12 @@ on_load
#
# R14A.
#
-recv_mark f
+# Modified in OTP 21 because it turns out that we don't need the
+# label after all.
+#
+
+recv_mark f => i_recv_mark
+i_recv_mark
recv_set Fail | label Lbl | loop_rec Lf Reg => \
i_recv_set | label Lbl | loop_rec Lf Reg