erts: Implement tracer modules

Add the possibility to use modules as trace data receivers. The functions
in the module have to be nifs as otherwise complex trace probes will be
very hard to handle (complex means trace probes for ports for example).

This commit changes the way that the ptab->tracer field works from always
being an immediate, to now be NIL if no tracer is present or else be
the tuple {TracerModule, TracerState} where TracerModule is an atom that
is later used to lookup the appropriate tracer callbacks to call and
TracerState is just passed to the tracer callback. The default process and
port tracers have been rewritten to use the new API.

This commit also changes the order which trace messages are delivered to the
potential tracer process. Any enif_send done in a tracer module may be delayed
indefinitely because of lock order issues. If a message is delayed any other
trace message send from that process is also delayed so that order is preserved
for each traced entity. This means that for some trace events (i.e. send/receive)
the events may come in an unintuitive order (receive before send) to the
trace receiver. Timestamps are taken when the trace message is generated so
trace messages from differented processes may arrive with the timestamp
out of order.

Both the erlang:trace and seq_trace:set_system_tracer accept the new tracer
module tracers and also the backwards compatible arguments.

OTP-10267

1 files changed, 45 insertions, 21 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 754e11f047..d633a982ca 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -123,15 +123,12 @@ static int insert_internal_link(Process* p, Eterm rpid)
 	erts_add_link(&ERTS_P_LINKS(p), LINK_PID, rp->common.id);
 	erts_add_link(&ERTS_P_LINKS(rp), LINK_PID, p->common.id);
 
-	ASSERT(is_nil(ERTS_TRACER_PROC(p))
-	       || is_internal_pid(ERTS_TRACER_PROC(p))
-	       || is_internal_port(ERTS_TRACER_PROC(p)));
+	ASSERT(IS_TRACER_VALID(ERTS_TRACER(p)));
 
 	if (IS_TRACED(p)) {
 	    if (ERTS_TRACE_FLAGS(p) & (F_TRACE_SOL|F_TRACE_SOL1))  {
 		ERTS_TRACE_FLAGS(rp) |= (ERTS_TRACE_FLAGS(p) & TRACEE_FLAGS);
-		ERTS_TRACER_PROC(rp) = ERTS_TRACER_PROC(p); /* maybe steal */
-
+                erts_tracer_replace(&rp->common, ERTS_TRACER(p));
 		if (ERTS_TRACE_FLAGS(p) & F_TRACE_SOL1) { /* maybe override */
 		    ERTS_TRACE_FLAGS(rp) &= ~(F_TRACE_SOL1 | F_TRACE_SOL);
 		    ERTS_TRACE_FLAGS(p) &= ~(F_TRACE_SOL1 | F_TRACE_SOL);
@@ -140,7 +137,8 @@ static int insert_internal_link(Process* p, Eterm rpid)
 	}
     }
     if (IS_TRACED_FL(rp, F_TRACE_PROCS))
-	trace_proc(p, rp, am_getting_linked, p->common.id);
+	trace_proc(p, p == rp ? rp_locks : ERTS_PROC_LOCK_MAIN|ERTS_PROC_LOCK_LINK,
+                   rp, am_getting_linked, p->common.id);
 
     if (p == rp)
 	erts_smp_proc_unlock(p, rp_locks & ~ERTS_PROC_LOCK_MAIN);
@@ -159,7 +157,7 @@ BIF_RETTYPE link_1(BIF_ALIST_1)
     DistEntry *dep;
 
     if (IS_TRACED_FL(BIF_P, F_TRACE_PROCS)) {
-	trace_proc(BIF_P, BIF_P, am_link, BIF_ARG_1);
+	trace_proc(BIF_P, ERTS_PROC_LOCK_MAIN, BIF_P, am_link, BIF_ARG_1);
     }
     /* check that the pid or port which is our argument is OK */
 
@@ -613,7 +611,7 @@ erts_queue_monitor_message(Process *p,
     ref_copy    = copy_struct(ref, ref_size, &hp, ohp);
 
     tup = TUPLE5(hp, am_DOWN, ref_copy, type, item_copy, reason_copy);
-    erts_queue_message(p, p_locksp, msgp, tup, NIL);
+    erts_queue_message(p, p_locksp, msgp, tup);
 }
 
 static BIF_RETTYPE
@@ -1001,6 +999,7 @@ BIF_RETTYPE unlink_1(BIF_ALIST_1)
     Process *rp;
     DistEntry *dep;
     ErtsLink *l = NULL, *rl = NULL;
+    ErtsProcLocks cp_locks = ERTS_PROC_LOCK_MAIN;
 
     /*
      * SMP specific note concerning incoming exit signals:
@@ -1015,7 +1014,7 @@ BIF_RETTYPE unlink_1(BIF_ALIST_1)
      */
 
     if (IS_TRACED_FL(BIF_P, F_TRACE_PROCS)) {
-	trace_proc(BIF_P, BIF_P, am_unlink, BIF_ARG_1);
+	trace_proc(BIF_P, cp_locks, BIF_P, am_unlink, BIF_ARG_1);
     }
 
     if (is_internal_port(BIF_ARG_1)) {
@@ -1120,10 +1119,10 @@ BIF_RETTYPE unlink_1(BIF_ALIST_1)
 
     erts_smp_proc_lock(BIF_P, ERTS_PROC_LOCK_LINK|ERTS_PROC_LOCK_STATUS);
 
+    cp_locks |= ERTS_PROC_LOCK_LINK|ERTS_PROC_LOCK_STATUS;
+
     /* get process struct */
-    rp = erts_pid2proc_opt(BIF_P, (ERTS_PROC_LOCK_MAIN
-				   | ERTS_PROC_LOCK_LINK
-				   | ERTS_PROC_LOCK_STATUS),
+    rp = erts_pid2proc_opt(BIF_P, cp_locks,
 			   BIF_ARG_1, ERTS_PROC_LOCK_LINK,
 			   ERTS_P2P_FLG_ALLOW_OTHER_X);
 
@@ -1149,14 +1148,17 @@ BIF_RETTYPE unlink_1(BIF_ALIST_1)
 	    erts_destroy_link(rl);
 
 	if (IS_TRACED_FL(rp, F_TRACE_PROCS) && rl != NULL) {
-	    trace_proc(BIF_P, rp, am_getting_unlinked, BIF_P->common.id);
+            erts_smp_proc_unlock(BIF_P, ERTS_PROC_LOCK_STATUS);
+            cp_locks &= ~ERTS_PROC_LOCK_STATUS;
+	    trace_proc(BIF_P, (ERTS_PROC_LOCK_MAIN | ERTS_PROC_LOCK_LINK),
+                       rp, am_getting_unlinked, BIF_P->common.id);
 	}
 
 	if (rp != BIF_P)
 	    erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
     }
  
-    erts_smp_proc_unlock(BIF_P, ERTS_PROC_LOCK_LINK|ERTS_PROC_LOCK_STATUS);
+    erts_smp_proc_unlock(BIF_P, cp_locks & ~ERTS_PROC_LOCK_MAIN);
 
     BIF_RET(am_true);
 
@@ -4337,12 +4339,34 @@ BIF_RETTYPE system_flag_2(BIF_ALIST_2)
     } else if (BIF_ARG_1 == am_trace_control_word) {
 	BIF_RET(db_set_trace_control_word(BIF_P, BIF_ARG_2));
     } else if (BIF_ARG_1 == am_sequential_tracer) {
-        Eterm old_value = erts_set_system_seq_tracer(BIF_P,
-						     ERTS_PROC_LOCK_MAIN,
-						     BIF_ARG_2);
-	if (old_value != THE_NON_VALUE) {
-	    BIF_RET(old_value);
-	}
+        ErtsTracer new_seq_tracer, old_seq_tracer;
+        Eterm ret;
+
+        if (BIF_ARG_2 == am_false)
+            new_seq_tracer = erts_tracer_nil;
+        else
+            new_seq_tracer = erts_term_to_tracer(THE_NON_VALUE, BIF_ARG_2);
+
+        if (new_seq_tracer == THE_NON_VALUE)
+            goto error;
+
+        old_seq_tracer = erts_set_system_seq_tracer(BIF_P,
+                                                    ERTS_PROC_LOCK_MAIN,
+                                                    new_seq_tracer);
+
+        ERTS_TRACER_CLEAR(&new_seq_tracer);
+
+        if (old_seq_tracer == THE_NON_VALUE)
+            goto error;
+
+        if (ERTS_TRACER_IS_NIL(old_seq_tracer))
+            BIF_RET(am_false);
+
+        ret = erts_tracer_to_term(BIF_P, old_seq_tracer);
+
+        ERTS_TRACER_CLEAR(&old_seq_tracer);
+
+        BIF_RET(ret);
     } else if (BIF_ARG_1 == make_small(1)) {
 	int i, max;
 	ErtsMessage* mp;
@@ -4679,7 +4703,7 @@ skip_current_msgq(Process *c_p)
 	res = 0;
     }
     else {
-	ERTS_SMP_MSGQ_MV_INQ2PRIVQ(c_p);
+        ERTS_SMP_MSGQ_MV_INQ2PRIVQ(c_p);
 	c_p->msg.save = c_p->msg.last;
 	res = 1;
     }