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, 29 insertions, 45 deletions

diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c
index be14386b14..76b96637ae 100644
--- a/erts/emulator/beam/erl_db_util.c
+++ b/erts/emulator/beam/erl_db_util.c
@@ -135,21 +135,22 @@ get_proc(Process *cp, Uint32 cp_locks, Eterm id, Uint32 id_locks)
 
 
 static Eterm
-set_tracee_flags(Process *tracee_p, Eterm tracer, Uint d_flags, Uint e_flags) {
+set_tracee_flags(Process *tracee_p, ErtsTracer tracer,
+                 Uint d_flags, Uint e_flags) {
     Eterm ret;
     Uint flags;
 
-    if (tracer == NIL) {
+    if (ERTS_TRACER_IS_NIL(tracer)) {
 	flags = ERTS_TRACE_FLAGS(tracee_p) & ~TRACEE_FLAGS;
     }  else {
 	flags = ((ERTS_TRACE_FLAGS(tracee_p) & ~d_flags) | e_flags);
-	if (! flags) tracer = NIL;
+	if (! flags) tracer = erts_tracer_nil;
     }
-    ret = ((ERTS_TRACER_PROC(tracee_p) != tracer
+    ret = ((!ERTS_TRACER_COMPARE(ERTS_TRACER(tracee_p),tracer)
 	    || ERTS_TRACE_FLAGS(tracee_p) != flags)
 	   ? am_true
 	   : am_false);
-    ERTS_TRACER_PROC(tracee_p) = tracer;
+    erts_tracer_replace(&tracee_p->common, tracer);
     ERTS_TRACE_FLAGS(tracee_p) = flags;
     return ret;
 }
@@ -163,40 +164,16 @@ set_tracee_flags(Process *tracee_p, Eterm tracer, Uint d_flags, Uint e_flags) {
 ** returns fail_term on failure. Fails if tracer pid or port is invalid.
 */
 static Eterm 
-set_match_trace(Process *tracee_p, Eterm fail_term, Eterm tracer,
+set_match_trace(Process *tracee_p, Eterm fail_term, ErtsTracer tracer,
 		Uint d_flags, Uint e_flags) {
-    Eterm ret = fail_term;
-    Process *tracer_p;
-    
-    ERTS_SMP_LC_ASSERT(ERTS_PROC_LOCKS_ALL == 
-		       erts_proc_lc_my_proc_locks(tracee_p));
-
-    if (is_internal_pid(tracer)
-	&& (tracer_p = 
-	    erts_pid2proc(tracee_p, ERTS_PROC_LOCKS_ALL,
-			  tracer, ERTS_PROC_LOCKS_ALL))) {
-	if (tracee_p != tracer_p) {
-	    ret = set_tracee_flags(tracee_p, tracer, d_flags, e_flags);
-	    ERTS_TRACE_FLAGS(tracer_p) |= (ERTS_TRACE_FLAGS(tracee_p)
-					   ? F_TRACER
-					   : 0);
-	    erts_smp_proc_unlock(tracer_p, ERTS_PROC_LOCKS_ALL);
-	}
-    } else if (is_internal_port(tracer)) {
-	Port *tracer_port = 
-	    erts_id2port_sflgs(tracer,
-			       tracee_p,
-			       ERTS_PROC_LOCKS_ALL,
-			       ERTS_PORT_SFLGS_INVALID_TRACER_LOOKUP);
-	if (tracer_port) {
-	    ret = set_tracee_flags(tracee_p, tracer, d_flags, e_flags);
-	    erts_port_release(tracer_port);
-	}
-    } else {
-	ASSERT(is_nil(tracer));
-	ret = set_tracee_flags(tracee_p, tracer, d_flags, e_flags);
-    }
-    return ret;
+
+    ERTS_SMP_LC_ASSERT(
+        ERTS_PROC_LOCKS_ALL == erts_proc_lc_my_proc_locks(tracee_p)
+        || erts_thr_progress_is_blocking());
+
+    if (ERTS_TRACER_IS_NIL(tracer) || erts_is_tracer_enabled(tracee_p, tracer))
+        return set_tracee_flags(tracee_p, tracer, d_flags, e_flags);
+    return fail_term;
 }
 
 /*
@@ -2358,7 +2335,7 @@ restart:
 	case matchEnableTrace:
 	    if ( (n = erts_trace_flag2bit(esp[-1]))) {
 		BEGIN_ATOMIC_TRACE(c_p);
-		set_tracee_flags(c_p, ERTS_TRACER_PROC(c_p), 0, n);
+		set_tracee_flags(c_p, ERTS_TRACER(c_p), 0, n);
 		esp[-1] = am_true;
 	    } else {
 		esp[-1] = FAIL_TERM;
@@ -2371,7 +2348,7 @@ restart:
 		BEGIN_ATOMIC_TRACE(c_p);
 		if ( (tmpp = get_proc(c_p, 0, esp[0], 0))) {
 		    /* Always take over the tracer of the current process */
-		    set_tracee_flags(tmpp, ERTS_TRACER_PROC(c_p), 0, n);
+		    set_tracee_flags(tmpp, ERTS_TRACER(c_p), 0, n);
 		    esp[-1] = am_true;
 		}
 	    }
@@ -2379,7 +2356,7 @@ restart:
 	case matchDisableTrace:
 	    if ( (n = erts_trace_flag2bit(esp[-1]))) {
 		BEGIN_ATOMIC_TRACE(c_p);
-		set_tracee_flags(c_p, ERTS_TRACER_PROC(c_p), n, 0);
+		set_tracee_flags(c_p, ERTS_TRACER(c_p), n, 0);
 		esp[-1] = am_true;
 	    } else {
 		esp[-1] = FAIL_TERM;
@@ -2392,7 +2369,7 @@ restart:
 		BEGIN_ATOMIC_TRACE(c_p);
 		if ( (tmpp = get_proc(c_p, 0, esp[0], 0))) {
 		    /* Always take over the tracer of the current process */
-		    set_tracee_flags(tmpp, ERTS_TRACER_PROC(c_p), n, 0);
+		    set_tracee_flags(tmpp, ERTS_TRACER(c_p), n, 0);
 		    esp[-1] = am_true;
 		}
 	    }
@@ -2428,7 +2405,7 @@ restart:
 	    {
 		/*    disable         enable                                */
 		Uint  d_flags  = 0,   e_flags  = 0;  /* process trace flags */
-		Eterm tracer = ERTS_TRACER_PROC(c_p);
+		ErtsTracer tracer = erts_tracer_nil;
 		/* XXX Atomicity note: Not fully atomic. Default tracer
 		 * is sampled from current process but applied to
 		 * tracee and tracer later after releasing main
@@ -2440,29 +2417,34 @@ restart:
 		 * {trace,[],[{{tracer,Tracer}}]} is much, much older.
 		 */
 		int   cputs = 0;
+                erts_tracer_update(&tracer, ERTS_TRACER(c_p));
 		
 		if (! erts_trace_flags(esp[-1], &d_flags, &tracer, &cputs) ||
 		    ! erts_trace_flags(esp[-2], &e_flags, &tracer, &cputs) ||
 		    cputs ) {
 		    (--esp)[-1] = FAIL_TERM;
+                    ERTS_TRACER_CLEAR(&tracer);
 		    break;
 		}
 		erts_smp_proc_lock(c_p, ERTS_PROC_LOCKS_ALL_MINOR);
 		(--esp)[-1] = set_match_trace(c_p, FAIL_TERM, tracer,
 					      d_flags, e_flags);
 		erts_smp_proc_unlock(c_p, ERTS_PROC_LOCKS_ALL_MINOR);
+                ERTS_TRACER_CLEAR(&tracer);
 	    }
 	    break;
 	case matchTrace3:
 	    {
 		/*    disable         enable                                */
 		Uint  d_flags  = 0,   e_flags  = 0;  /* process trace flags */
-		Eterm tracer = ERTS_TRACER_PROC(c_p);
+		ErtsTracer tracer = erts_tracer_nil;
 		/* XXX Atomicity note. Not fully atomic. See above. 
 		 * Above it could possibly be solved, but not here.
 		 */
 		int   cputs = 0;
 		Eterm tracee = (--esp)[0];
+
+                erts_tracer_update(&tracer, ERTS_TRACER(c_p));
 		
 		if (! erts_trace_flags(esp[-1], &d_flags, &tracer, &cputs) ||
 		    ! erts_trace_flags(esp[-2], &e_flags, &tracer, &cputs) ||
@@ -2470,6 +2452,7 @@ restart:
 		    ! (tmpp = get_proc(c_p, ERTS_PROC_LOCK_MAIN, 
 				       tracee, ERTS_PROC_LOCKS_ALL))) {
 		    (--esp)[-1] = FAIL_TERM;
+                    ERTS_TRACER_CLEAR(&tracer);
 		    break;
 		}
 		if (tmpp == c_p) {
@@ -2483,6 +2466,7 @@ restart:
 		    erts_smp_proc_unlock(tmpp, ERTS_PROC_LOCKS_ALL);
 		    erts_smp_proc_lock(c_p, ERTS_PROC_LOCK_MAIN);
 		}
+                ERTS_TRACER_CLEAR(&tracer);
 	    }
 	    break;
 	case matchCatch:  /* Match success, now build result */
@@ -5084,7 +5068,7 @@ static Eterm match_spec_test(Process *p, Eterm against, Eterm spec, int trace)
 	lint_res = db_match_set_lint(p, spec, DCOMP_TABLE | DCOMP_FAKE_DESTRUCTIVE);
 	mps = db_match_set_compile(p, spec, DCOMP_TABLE | DCOMP_FAKE_DESTRUCTIVE);
     }
-    
+
     if (mps == NULL) {
 	hp = HAlloc(p,3);
 	ret = TUPLE2(hp, am_error, lint_res);