Update dtrace for changes in R15

22 files changed, 216 insertions, 188 deletions

diff --git a/README.dtrace.md b/README.dtrace.md
index 71023dfe69..bbff233ed9 100644
--- a/README.dtrace.md
+++ b/README.dtrace.md
@@ -27,27 +27,17 @@ Goals
 Supported platforms
 -------------------
 
-The autoconf procedure is supported, I believe, for OS X/Snow Leopard
-and OpenSolaris/64-bit.  Just add the `--enable-dtrace` option your
-command to run the `configure` script.
-
-The code has been only very lightly tested on OS X.  It ought to
-compile on a Solaris 10 or OpenSolaris machine, but no promises yet.
-
-The autoconf stuff is ugly right now.  It could use some cleaning up.
-For example:
-
-* After editing the `erlang_dtrace.d` file, you need to re-run the
-* top-level "configure" script in order to update `erlang_dtrace.h`.
-* `make clean` will remove `erlang_dtrace.h`.  A build will fail
-  unless the top-level "configure" script is re-run to re-create that
-  file.
-* The `erlang_dtrace.h` file's location should probably be moved to an
-  OTP platform-specific build dir, for example,
-  `path/to/somewhere/i386-apple-darwin10.8.0`
-* There are probably some other build by-products that are also being
-  put into the "wrong" directory, for example, `erlang_dtrace.o` for
-  Solaris platforms.
+* OS X 10.6.x / Snow Leopard.  It should also work for 10.7 / Lion,
+  but I haven't personally tested it.
+* Solaris 10.  I have done limited testing on Solaris 11 and
+  OpenIndiana release 151a, and both appear to work.
+* FreeBSD 9.0, though please see the "FreeBSD 9.0 Release Notes"
+  section below!
+* Linux via SystemTap compatibility.  Please see the file
+  `README.systemtap.md` for more details.
+
+Just add the `--enable-dtrace` option to your command when you run the
+`configure` script.
 
 Contributions
 -------------
@@ -61,9 +51,12 @@ To build from scratch, use this recipe.  If you're an experienced Git
 user and wish to add my repository as a remote repository, be my
 guest.  Just resume the recipe at command #4.
 
+NOTE: The `dtrace-experiment+michal2` branch is used for changes that
+can be applied to both R14B and R15 releases.
+
     % git clone git://github.com/slfritchie/otp.git
     % cd otp
-    % git checkout -b dtrace-experiment origin/dtrace-experiment
+    % git checkout -b dtrace-experiment+michal2 origin/dtrace-experiment+michal2
     % env ERL_TOP=`pwd` ./otp_build autoconf
     % env ERL_TOP=`pwd` ./configure --enable-dtrace + whatever args you need
     % env ERL_TOP=`pwd` make
diff --git a/erts/emulator/Makefile.in b/erts/emulator/Makefile.in
index 3fb0964810..d8fad98de2 100644
--- a/erts/emulator/Makefile.in
+++ b/erts/emulator/Makefile.in
@@ -486,7 +486,11 @@ endif
 endif
 
 ifdef DTRACE_ENABLED
-GENERATE += $(TARGET)/erlang_dtrace.h
+# global.h causes problems by including dtrace-wrapper.h which includes
+# the autogenerated erlang_dtrace.h ... so make erlang_dtrace.h very early.
+generate: $(TARGET)/erlang_dtrace.h $(GENERATE)
+else
+generate: $(GENERATE)
 endif
 
 ifdef HIPE_ENABLED
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index d0beccfda2..1dbe2cad00 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -41,8 +41,6 @@
 #include "hipe_mode_switch.h"
 #include "hipe_bif1.h"
 #endif
-
-#include <assert.h>
 #include "dtrace-wrapper.h"
 
 /* #define HARDDEBUG 1 */
@@ -1053,72 +1051,6 @@ init_emulator(void)
 #  define REG_tmp_arg2
 #endif
 
-ERTS_INLINE void
-dtrace_proc_str(Process *process, char *process_buf)
-{
-    dtrace_pid_str(process->id, process_buf);
-}
-
-ERTS_INLINE void
-dtrace_pid_str(Eterm pid, char *process_buf)
-{
-    snprintf(process_buf, DTRACE_TERM_BUF_SIZE, "<%lu.%lu.%lu>",
-             pid_channel_no(pid),
-             pid_number(pid),
-             pid_serial(pid));
-}
-
-ERTS_INLINE void
-dtrace_port_str(Port *port, char *port_buf)
-{
-    snprintf(port_buf, DTRACE_TERM_BUF_SIZE, "#Port<%lu.%lu>",
-             port_channel_no(port->id),
-             port_number(port->id));
-}
-
-ERTS_INLINE void
-dtrace_drvport_str(ErlDrvPort drvport, char *port_buf)
-{
-    Port *port = erts_drvport2port(drvport);
-
-    snprintf(port_buf, DTRACE_TERM_BUF_SIZE, "#Port<%lu.%lu>",
-             port_channel_no(port->id),
-             port_number(port->id));
-}
-
-ERTS_INLINE void
-dtrace_fun_decode(Process *process,
-                  Eterm module, Eterm function, int arity,
-                  char *process_buf, char *mfa_buf)
-{
-    char funbuf[DTRACE_TERM_BUF_SIZE];
-    char *funptr = funbuf;
-    char *p = NULL;
-
-    if (process_buf) {
-        dtrace_proc_str(process, process_buf);
-    }
-
-    erts_snprintf(funbuf, sizeof(funbuf), "%T", function);
-    /*
-     * I'm not quite sure how these function names are synthesized,
-     *  but they almost always seem to be in the form of
-     *  '-name/arity-fun-0-' so I'm chopping them up when it's -fun-0-
-     *  (which seems to be the toplevel)
-     */
-    if (funbuf[0] == '\'' && funbuf[1] == '-'
-        && strlen(funbuf) > 3 && funbuf[strlen(funbuf) - 3] == '0') {
-        p = strchr(funbuf, '/');
-        if (p) {
-            *p = 0;
-        }
-        funptr += 2;
-    }
-
-    erts_snprintf(mfa_buf, DTRACE_TERM_BUF_SIZE, "%T:%s/%d",
-                  module, funptr, arity);
-}
-
 #ifdef HAVE_DTRACE
 
 #define DTRACE_CALL(p, m, f, a)                                 \
@@ -1190,6 +1122,16 @@ dtrace_fun_decode(Process *process,
 
 #endif /* HAVE_DTRACE */
 
+void
+dtrace_drvport_str(ErlDrvPort drvport, char *port_buf)
+{
+    Port *port = erts_drvport2port(drvport);
+
+    erts_snprintf(port_buf, DTRACE_TERM_BUF_SIZE, "#Port<%lu.%lu>",
+                  port_channel_no(port->id),
+                  port_number(port->id));
+}
+
 /*
  * process_main() is called twice:
  * The first call performs some initialisation, including exporting
@@ -1376,7 +1318,8 @@ void process_main(void)
                                       (Eterm)fptr[1], (Uint)fptr[2],
                                       NULL, fun_buf);
                 } else {
-                    snprintf(fun_buf, sizeof(fun_buf), "<unknown/%p>", next);
+                    erts_snprintf(fun_buf, sizeof(fun_buf),
+                                  "<unknown/%p>", next);
                 }
             }
 
@@ -1970,7 +1913,9 @@ void process_main(void)
      if (DTRACE_ENABLED(message_receive)) {
          Eterm token2 = NIL;
          DTRACE_CHARBUF(receiver_name, DTRACE_TERM_BUF_SIZE);
-         Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
+         ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+         ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+         ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
 
          dtrace_proc_str(c_p, receiver_name);
          token2 = SEQ_TRACE_TOKEN(c_p);
diff --git a/erts/emulator/beam/dist.c b/erts/emulator/beam/dist.c
index 6f6b04d278..ba55a1918a 100644
--- a/erts/emulator/beam/dist.c
+++ b/erts/emulator/beam/dist.c
@@ -741,8 +741,10 @@ erts_dsig_send_msg(ErtsDSigData *dsdp, Eterm remote, Eterm message)
     Eterm token = NIL;
     Process *sender = dsdp->proc;
     int res;
-    Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
-    Uint msize = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
+    ERTS_DECLARE_DUMMY(Uint msize) = 0;
     DTRACE_CHARBUF(node_name, 64);
     DTRACE_CHARBUF(sender_name, 64);
     DTRACE_CHARBUF(receiver_name, 64);
@@ -788,8 +790,10 @@ erts_dsig_send_reg_msg(ErtsDSigData *dsdp, Eterm remote_name, Eterm message)
     Eterm token = NIL;
     Process *sender = dsdp->proc;
     int res;
-    Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
-    Uint32 msize = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
+    ERTS_DECLARE_DUMMY(Uint32 msize) = 0;
     DTRACE_CHARBUF(node_name, 64);
     DTRACE_CHARBUF(sender_name, 64);
     DTRACE_CHARBUF(receiver_name, 128);
@@ -838,7 +842,9 @@ erts_dsig_send_exit_tt(ErtsDSigData *dsdp, Eterm local, Eterm remote,
     DeclareTmpHeapNoproc(ctl_heap,6);
     int res;
     Process *sender = dsdp->proc;
-    Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
     DTRACE_CHARBUF(node_name, 64);
     DTRACE_CHARBUF(sender_name, 64);
     DTRACE_CHARBUF(remote_name, 128);
diff --git a/erts/emulator/beam/dtrace-wrapper.h b/erts/emulator/beam/dtrace-wrapper.h
index f93871bd25..b633058e90 100644
--- a/erts/emulator/beam/dtrace-wrapper.h
+++ b/erts/emulator/beam/dtrace-wrapper.h
@@ -23,15 +23,6 @@
 
 #define DTRACE_TERM_BUF_SIZE 256
 
-#ifndef	DTRACE_DRIVER_SKIP_FUNC_DECLARATIONS
-inline void dtrace_proc_str(Process *process, char *process_buf);
-inline void dtrace_pid_str(Eterm pid, char *process_buf);
-inline void dtrace_port_str(Port *port, char *port_buf);
-inline void dtrace_fun_decode(Process *process,
-			      Eterm module, Eterm function, int arity,
-			      char *process_buf, char *mfa_buf);
-#endif
-
 /*
  * Some varieties of SystemTap macros do not like statically-sized
  * char[N] buffers.  (For example, CentOS 6's macros.)
diff --git a/erts/emulator/beam/erl_async.c b/erts/emulator/beam/erl_async.c
index 72dcc99f4f..b8cb3c6cc4 100644
--- a/erts/emulator/beam/erl_async.c
+++ b/erts/emulator/beam/erl_async.c
@@ -253,8 +253,7 @@ erts_get_async_ready_queue(Uint sched_id)
 
 static ERTS_INLINE void async_add(ErtsAsync *a, ErtsAsyncQ* q)
 {
-    /* DTRACE TODO: Get the queue length from erts_thr_q_enqueue() */
-    int len = -1;
+    int len;
 
     if (is_internal_port(a->port)) {
 #if ERTS_USE_ASYNC_READY_Q
@@ -275,6 +274,8 @@ static ERTS_INLINE void async_add(ErtsAsync *a, ErtsAsyncQ* q)
         DTRACE_CHARBUF(port_str, 16);
 
         erts_snprintf(port_str, sizeof(port_str), "%T", a->port);
+        /* DTRACE TODO: Get the queue length from erts_thr_q_enqueue() ? */
+        len = -1;
         DTRACE2(aio_pool_add, port_str, len);
     }
     gcc_optimizer_hack++;
@@ -288,8 +289,7 @@ static ERTS_INLINE ErtsAsync *async_get(ErtsThrQ_t *q,
     int saved_fin_deq = 0;
     ErtsThrQFinDeQ_t fin_deq;
 #endif
-    /* DTRACE TODO: Get the queue length from erts_thr_q_dequeue() somehow? */
-    int len = -1;
+    int len;
 
     while (1) {
 	ErtsAsync *a = (ErtsAsync *) erts_thr_q_dequeue(q);
@@ -305,6 +305,8 @@ static ERTS_INLINE ErtsAsync *async_get(ErtsThrQ_t *q,
                 DTRACE_CHARBUF(port_str, 16);
 
                 erts_snprintf(port_str, sizeof(port_str), "%T", a->port);
+                /* DTRACE TODO: Get the length from erts_thr_q_dequeue() ? */
+                len = -1;
                 DTRACE2(aio_pool_get, port_str, len);
             }
 	    return a;
diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index 858ae32ad5..679a3645ba 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -2055,7 +2055,6 @@ shrink_new_heap(Process *p, Uint new_sz, Eterm *objv, int nobj)
     Uint heap_size = HEAP_TOP(p) - HEAP_START(p);
     Sint offs;
     Uint stack_size = p->hend - p->stop;
-    char pidbuf[DTRACE_TERM_BUF_SIZE];
 
     ASSERT(new_sz < p->heap_sz);
     sys_memmove(p->heap + new_sz - stack_size, p->stop, stack_size *
diff --git a/erts/emulator/beam/erl_message.c b/erts/emulator/beam/erl_message.c
index 8489353c9e..786d6ac52c 100644
--- a/erts/emulator/beam/erl_message.c
+++ b/erts/emulator/beam/erl_message.c
@@ -336,7 +336,9 @@ erts_queue_dist_message(Process *rcvr,
 			Eterm token)
 {
     ErlMessage* mp;
-    Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
 #ifdef ERTS_SMP
     ErtsProcLocks need_locks;
 #endif
@@ -495,7 +497,9 @@ erts_queue_message(Process* receiver,
 
     if (DTRACE_ENABLED(message_queued)) {
         DTRACE_CHARBUF(receiver_name, DTRACE_TERM_BUF_SIZE);
-        Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
+        ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+        ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+        ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
 
         dtrace_proc_str(receiver, receiver_name);
         if (seq_trace_token != NIL && is_tuple(seq_trace_token)) {
@@ -822,7 +826,9 @@ erts_send_message(Process* sender,
     Eterm token = NIL;
     DTRACE_CHARBUF(sender_name, 64);
     DTRACE_CHARBUF(receiver_name, 64);
-    Sint tok_label = 0, tok_lastcnt = 0, tok_serial = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_label) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_lastcnt) = 0;
+    ERTS_DECLARE_DUMMY(Sint tok_serial) = 0;
 
     BM_STOP_TIMER(system);
     BM_MESSAGE(message,sender,receiver);
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 6f6263d160..7f12004b43 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -1072,13 +1072,6 @@ void process_main(void);
 Eterm build_stacktrace(Process* c_p, Eterm exc);
 Eterm expand_error_value(Process* c_p, Uint freason, Eterm Value);
 void erts_save_stacktrace(Process* p, struct StackTrace* s, int depth);
-ERTS_INLINE void dtrace_proc_str(Process *process, char *process_buf);
-ERTS_INLINE void dtrace_pid_str(Eterm pid, char *process_buf);
-ERTS_INLINE void dtrace_port_str(Port *port, char *port_buf);
-ERTS_INLINE void dtrace_drvport_str(ErlDrvPort port, char *port_buf);
-ERTS_INLINE void dtrace_fun_decode(Process *process,
-                                   Eterm module, Eterm function, int arity,
-                                   char *process_buf, char *mfa_buf);
 
 /* erl_init.c */
 
@@ -1981,4 +1974,66 @@ erts_alloc_message_heap(Uint size,
 #  define UseTmpHeapNoproc(Size) /* Nothing */
 #  define UnUseTmpHeapNoproc(Size) /* Nothing */
 #endif /* HEAP_ON_C_STACK */
+
+#if ERTS_GLB_INLINE_INCL_FUNC_DEF
+
+#include "dtrace-wrapper.h"
+
+ERTS_GLB_INLINE void
+dtrace_pid_str(Eterm pid, char *process_buf)
+{
+    erts_snprintf(process_buf, DTRACE_TERM_BUF_SIZE, "<%lu.%lu.%lu>",
+                  pid_channel_no(pid),
+                  pid_number(pid),
+                  pid_serial(pid));
+}
+
+ERTS_GLB_INLINE void
+dtrace_proc_str(Process *process, char *process_buf)
+{
+    dtrace_pid_str(process->id, process_buf);
+}
+
+ERTS_GLB_INLINE void
+dtrace_port_str(Port *port, char *port_buf)
+{
+    erts_snprintf(port_buf, DTRACE_TERM_BUF_SIZE, "#Port<%lu.%lu>",
+                  port_channel_no(port->id),
+                  port_number(port->id));
+}
+
+ERTS_GLB_INLINE void
+dtrace_fun_decode(Process *process,
+                  Eterm module, Eterm function, int arity,
+                  char *process_buf, char *mfa_buf)
+{
+    char funbuf[DTRACE_TERM_BUF_SIZE];
+    char *funptr = funbuf;
+    char *p = NULL;
+
+    if (process_buf) {
+        dtrace_proc_str(process, process_buf);
+    }
+
+    erts_snprintf(funbuf, sizeof(funbuf), "%T", function);
+    /*
+     * I'm not quite sure how these function names are synthesized,
+     *  but they almost always seem to be in the form of
+     *  '-name/arity-fun-0-' so I'm chopping them up when it's -fun-0-
+     *  (which seems to be the toplevel)
+     */
+    if (funbuf[0] == '\'' && funbuf[1] == '-'
+        && strlen(funbuf) > 3 && funbuf[strlen(funbuf) - 3] == '0') {
+        p = strchr(funbuf, '/');
+        if (p) {
+            *p = 0;
+        }
+        funptr += 2;
+    }
+
+    erts_snprintf(mfa_buf, DTRACE_TERM_BUF_SIZE, "%T:%s/%d",
+                  module, funptr, arity);
+}
+#endif /* #if ERTS_GLB_INLINE_INCL_FUNC_DEF */
+
 #endif /* !__GLOBAL_H__ */
diff --git a/erts/emulator/drivers/common/efile_drv.c b/erts/emulator/drivers/common/efile_drv.c
index b72f95792c..293f024e45 100644
--- a/erts/emulator/drivers/common/efile_drv.c
+++ b/erts/emulator/drivers/common/efile_drv.c
@@ -112,7 +112,6 @@
 #include "erl_threads.h"
 #include "zlib.h"
 #include "gzio.h"
-#define DTRACE_DRIVER_SKIP_FUNC_DECLARATIONS
 #include "dtrace-wrapper.h"
 #include <ctype.h>
 #include <sys/types.h>
@@ -126,6 +125,8 @@ static unsigned gcc_optimizer_hack = 0;
 
 #ifdef  HAVE_DTRACE
 
+#define DTRACE_EFILE_BUFSIZ 128
+
 #define DTRACE_INVOKE_SETUP(op) \
     do { DTRACE3(efile_drv_int_entry, d->sched_i1, d->sched_i2, op); } while (0)
 #define DTRACE_INVOKE_SETUP_BY_NAME(op) \
@@ -149,6 +150,7 @@ typedef struct {
 dt_private *get_dt_private(int);
 #else  /* HAVE_DTRACE */
 typedef struct {
+    char        dummy;          /* Unused except to quiet some compilers */
 } dt_private;
 
 #define DTRACE_INVOKE_SETUP(op)            do {} while (0)
@@ -429,7 +431,7 @@ struct t_data
 #ifdef  HAVE_DTRACE
     int               sched_i1;
     Uint64            sched_i2;
-    char              sched_utag[128+1];
+    char              sched_utag[DTRACE_EFILE_BUFSIZ+1];
 #else
     char              sched_utag[1];
 #endif
@@ -2196,12 +2198,12 @@ file_async_ready(ErlDrvData e, ErlDrvThreadData data)
     int sched_i1 = d->sched_i1, sched_i2 = d->sched_i2, command = d->command,
         result_ok = d->result_ok,
         posix_errno = d->result_ok ? 0 : d->errInfo.posix_errno;
-    DTRACE_CHARBUF(sched_utag, 128+1);
+    DTRACE_CHARBUF(sched_utag, DTRACE_EFILE_BUFSIZ+1);
 
     sched_utag[0] = '\0';
     if (DTRACE_ENABLED(efile_drv_return)) {
-        strncpy(sched_utag, d->sched_utag, sizeof(sched_utag) - 1);
-        sched_utag[sizeof(sched_utag) - 1] = '\0';
+        strncpy(sched_utag, d->sched_utag, DTRACE_EFILE_BUFSIZ);
+        sched_utag[DTRACE_EFILE_BUFSIZ] = '\0';
     }
 #endif  /* HAVE_DTRACE */
 
@@ -2488,8 +2490,12 @@ file_output(ErlDrvData e, char* buf, ErlDrvSizeT count)
     char* name;			/* Points to the filename in buf. */
     int command;
     struct t_data *d = NULL;
-    char *dt_utag = NULL, *dt_s1 = NULL, *dt_s2 = NULL;
-    Sint64 dt_i1 = 0, dt_i2 = 0, dt_i3 = 0, dt_i4 = 0;
+    ERTS_DECLARE_DUMMY(char *dt_utag) = NULL;
+    char *dt_s1 = NULL, *dt_s2 = NULL;
+    ERTS_DECLARE_DUMMY(Sint64 dt_i1) = 0;
+    ERTS_DECLARE_DUMMY(Sint64 dt_i2) = 0;
+    ERTS_DECLARE_DUMMY(Sint64 dt_i3) = 0;
+    ERTS_DECLARE_DUMMY(Sint64 dt_i4) = 0;
 #ifdef  HAVE_DTRACE
     dt_private *dt_priv = get_dt_private(0);
 #endif  /* HAVE_DTRACE */
@@ -3015,8 +3021,10 @@ file_outputv(ErlDrvData e, ErlIOVec *ev) {
     int p, q;
     int err;
     struct t_data *d = NULL;
-    Sint64 dt_i1 = 0, dt_i2 = 0, dt_i3 = 0, dt_i4 = 0;
-    char *dt_utag = NULL, *dt_s1 = NULL;
+    Sint64 dt_i1 = 0, dt_i2 = 0, dt_i3 = 0;
+    ERTS_DECLARE_DUMMY(Sint64 dt_i4) = 0;
+    char *dt_utag = NULL;
+    ERTS_DECLARE_DUMMY(char *dt_s1) = NULL;
 #ifdef  HAVE_DTRACE
     dt_private *dt_priv = get_dt_private(dt_driver_io_worker_base);
 #else
diff --git a/erts/lib_src/common/erl_printf.c b/erts/lib_src/common/erl_printf.c
index afb9c0abb7..399c83384e 100644
--- a/erts/lib_src/common/erl_printf.c
+++ b/erts/lib_src/common/erl_printf.c
@@ -173,10 +173,10 @@ typedef struct {
 static int
 write_sn(void *vwsnap, char* buf, size_t len)
 {
+    int rv = 0;
     write_sn_arg_t *wsnap = (write_sn_arg_t *) vwsnap;
     ASSERT(wsnap);
     ASSERT(len > 0);
-    int rv = 0;
     if (wsnap->len > 0) {
 	size_t sz = len;
 	if (sz >= wsnap->len)
diff --git a/erts/preloaded/ebin/prim_file.beam b/erts/preloaded/ebin/prim_file.beam
index 9d6c47ffc1..6778fe353c 100644
--- a/erts/preloaded/ebin/prim_file.beam
+++ b/erts/preloaded/ebin/prim_file.beam
diff --git a/erts/preloaded/src/prim_file.erl b/erts/preloaded/src/prim_file.erl
index 5c9cad3a2c..46ce3ab1a4 100644
--- a/erts/preloaded/src/prim_file.erl
+++ b/erts/preloaded/src/prim_file.erl
@@ -1493,19 +1493,15 @@ to_seconds({_,_} = Datetime, universal) ->
 to_seconds({_,_} = Datetime, local) ->
     erlang:universaltime_to_posixtime(erlang:localtime_to_universaltime(Datetime)).
 
-%% TODO: Duplicate code!
 get_dtrace_utag() ->
-    case get(dtrace_utag) of
-        X when is_list(X) ->
-            X;
-        _ ->
-            ""
+    %% We cannot call dtrace:get_utag() because this is prim_file.erl.
+    %% We must reimplement it here.
+    case get('_dtrace_utag_@_@') of
+        undefined ->
+            <<>>;
+        X ->
+            X
     end.
 
-%% TODO: Measure if it's worth checking (re:run()?) for NUL byte first?
-enc_utag([0|Cs]) ->
-    enc_utag(Cs);
-enc_utag([C|Cs]) ->
-    [C|enc_utag(Cs)];
-enc_utag([]) ->
-    [0].
+enc_utag(UTag) ->
+    [UTag, 0].
diff --git a/lib/dtrace/c_src/Makefile b/lib/dtrace/c_src/Makefile
index f3320bb766..a65491d45d 100644
--- a/lib/dtrace/c_src/Makefile
+++ b/lib/dtrace/c_src/Makefile
@@ -1,4 +1,4 @@
 #
-# Invoke with GNU make or clearmake -C gnu.
+# Invoke with GNU make
 #
 include $(ERL_TOP)/make/run_make.mk
diff --git a/lib/dtrace/c_src/Makefile.in b/lib/dtrace/c_src/Makefile.in
index ed13684a95..831ce5ce75 100644
--- a/lib/dtrace/c_src/Makefile.in
+++ b/lib/dtrace/c_src/Makefile.in
@@ -72,7 +72,7 @@ RELSYSDIR = $(RELEASE_PATH)/lib/dtrace-$(VSN)
 # ----------------------------------------------------
 # Misc Macros
 # ----------------------------------------------------
-OBJS = $(OBJDIR)/dtrace$(TYPEMARKER).o
+before_DTrace_OBJS = $(OBJDIR)/dtrace$(TYPEMARKER).o
 ## NIF_MAKEFILE = $(PRIVDIR)/Makefile
 
 # Higher-level makefiles says that we can only compile on UNIX flavors
@@ -100,18 +100,17 @@ else
 DTRACE_USER_HEADER=
 endif
 
+DTRACE_OBJS =
 ifdef DTRACE_ENABLED_2STEP
-OBJS += $(OBJDIR)/dtrace_user.o
-$(OBJDIR)/dtrace_user.o: $(OBJS) $(OBJDIR)/dtrace_user.h
-	touch $(OBJDIR)/erlang_dtrace.c
-	$(CC) $(CFLAGS) -c -o $@ $(OBJDIR)/erlang_dtrace.c
-	# The object file created above is immediately clobbered below.
-	# But creating it above avoids chicken-and-egg problem with OBJS
+DTRACE_OBJS += $(OBJDIR)/dtrace_user.o
+$(OBJDIR)/dtrace_user.o: $(before_DTrace_OBJS) $(OBJDIR)/dtrace_user.h
 	dtrace -G -C \
 	  -s ./dtrace_user.d \
-	  -o $@ $(OBJS)
+	  -o $@ $(before_DTrace_OBJS)
 endif
 
+OBJS = $(before_DTrace_OBJS) $(DTRACE_OBJS)
+
 $(OBJDIR):
 	-@mkdir -p $(OBJDIR)
 
diff --git a/lib/dtrace/c_src/dtrace.c b/lib/dtrace/c_src/dtrace.c
index c9d25ece9c..90bb39a4b8 100644
--- a/lib/dtrace/c_src/dtrace.c
+++ b/lib/dtrace/c_src/dtrace.c
@@ -25,7 +25,6 @@
 #include "erl_nif.h"
 #include "config.h"
 #include "sys.h"
-#define DTRACE_DRIVER_SKIP_FUNC_DECLARATIONS
 #include "dtrace-wrapper.h"
 #ifdef  HAVE_DTRACE
 #include "dtrace_user.h"
@@ -144,8 +143,7 @@ static ERL_NIF_TERM user_trace_i4s4(ErlNifEnv* env, int argc, const ERL_NIF_TERM
 
     if (DTRACE_ENABLED(user_trace_i4s4)) {
 	dtrace_nifenv_str(env, procbuf);
-        get_string_maybe(env, argv[0], &utbuf,
-                         user_tagbuf, sizeof(user_tagbuf)-1);
+        get_string_maybe(env, argv[0], &utbuf, user_tagbuf, MESSAGE_BUFSIZ);
         if (! enif_get_int64(env, argv[1], &i1))
             i1 = 0;
         if (! enif_get_int64(env, argv[2], &i2))
@@ -154,14 +152,10 @@ static ERL_NIF_TERM user_trace_i4s4(ErlNifEnv* env, int argc, const ERL_NIF_TERM
             i3 = 0;
         if (! enif_get_int64(env, argv[4], &i4))
             i4 = 0;
-        get_string_maybe(env, argv[5], &mbuf1,
-                         messagebuf1, sizeof(messagebuf1)-1);
-        get_string_maybe(env, argv[6], &mbuf2,
-                         messagebuf2, sizeof(messagebuf2)-1);
-        get_string_maybe(env, argv[7], &mbuf3,
-                         messagebuf3, sizeof(messagebuf3)-1);
-        get_string_maybe(env, argv[8], &mbuf4,
-                         messagebuf4, sizeof(messagebuf4)-1);
+        get_string_maybe(env, argv[5], &mbuf1, messagebuf1, MESSAGE_BUFSIZ);
+        get_string_maybe(env, argv[6], &mbuf2, messagebuf2, MESSAGE_BUFSIZ);
+        get_string_maybe(env, argv[7], &mbuf3, messagebuf3, MESSAGE_BUFSIZ);
+        get_string_maybe(env, argv[8], &mbuf4, messagebuf4, MESSAGE_BUFSIZ);
 	DTRACE10(user_trace_i4s4, procbuf, utbuf,
 		 i1, i2, i3, i4, mbuf1, mbuf2, mbuf3, mbuf4);
 	return atom_true;
diff --git a/lib/dtrace/examples/dist.d b/lib/dtrace/examples/dist.d
index f37c827f14..550e10d363 100644
--- a/lib/dtrace/examples/dist.d
+++ b/lib/dtrace/examples/dist.d
@@ -30,13 +30,13 @@ erlang*:::dist-port_busy
 {
     printf("dist port_busy: node %s, port %s, remote_node %s, blocked pid %s\n",
            copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), copyinstr(arg3));
-    blocked_procs[copyinstr(arg3)] = timestamp;
-}
-
-erlang*:::dist-port_busy
-{
-    printf("dist port_busy: node %s, port %s, remote_node %s, blocked pid %s\n",
-           copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), copyinstr(arg3));
+    /*
+     * For variable use advice, see:
+     *    http://dtrace.org/blogs/brendan/2011/11/25/dtrace-variable-types/
+     *
+     * Howevever, it's quite possible for the blocked events to span
+     * threads, so we'll use globals.
+     */
     blocked_procs[copyinstr(arg3)] = timestamp;
 }
 
diff --git a/lib/dtrace/examples/port1.d b/lib/dtrace/examples/port1.d
index b82e783a14..204abbd3b8 100644
--- a/lib/dtrace/examples/port1.d
+++ b/lib/dtrace/examples/port1.d
@@ -99,10 +99,12 @@ erlang*:::port-command
 
 erlang*:::port-control
 {
-    cmd = driver_map[copyinstr(arg2), arg3];
-    cmd_str = (cmd == 0) ? "unknown" : cmd;
+    /* http://dtrace.org/blogs/brendan/2011/11/25/dtrace-variable-types/ */
+    this->cmd = driver_map[copyinstr(arg2), arg3];
+    this->cmd_str = (this->cmd == 0) ? "unknown" : this->cmd;
     printf("port control pid %s port %s port name %s command %d %s\n",
-	   copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), arg3, cmd_str);
+	   copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), arg3,
+           this->cmd_str);
 }
 
 /* port-exit is fired as a result of port_close() or exit signal */
diff --git a/lib/dtrace/examples/process-scheduling.d b/lib/dtrace/examples/process-scheduling.d
index 9e31da2774..79e9cc598c 100644
--- a/lib/dtrace/examples/process-scheduling.d
+++ b/lib/dtrace/examples/process-scheduling.d
@@ -31,5 +31,5 @@ erlang*:::process-unscheduled
 erlang*:::process-hibernate
 {
     printf("  Hibernate pid %s resume mfa %s\n",
-     copyinstr(arg0), copyinstr(arg1));
+           copyinstr(arg0), copyinstr(arg1));
 }
diff --git a/lib/dtrace/src/dtrace.erl b/lib/dtrace/src/dtrace.erl
index 45addafc53..6951c03215 100644
--- a/lib/dtrace/src/dtrace.erl
+++ b/lib/dtrace/src/dtrace.erl
@@ -14,8 +14,8 @@
 %%% four integer arguments and four string arguments; the integer
 %%% argument(s) must come before any string argument.  For example:
 %%% ```
-%%% 1> put(dtrace_utag, "GGOOOAAALL!!!!!").
-%%% undefined
+%%% 1> dtrace:put_tag("GGOOOAAALL!!!!!").
+%%% true
 %%% 2> dtrace:init().
 %%% ok
 %%%
@@ -35,9 +35,13 @@
 %%% then the driver will ignore the user's input and use a default
 %%% value of 0 or NULL, respectively.
 
+-define(DTRACE_UT_KEY, '_dtrace_utag_@_@'). % Match prim_file:get_dtrace_utag()!
+
 -export([init/0, available/0,
          user_trace_s1/1, % TODO: unify with pid & tag args like user_trace_i4s4
          p/0, p/1, p/2, p/3, p/4, p/5, p/6, p/7, p/8]).
+-export([put_utag/1, get_utag/0]).
+
 -export([scaff/0]). % Development only
 -export([user_trace_i4s4/9]). % Know what you're doing!
 
@@ -68,7 +72,7 @@ available() ->
 
 -spec user_trace_s1(iolist()) -> true | false | error | badarg.
 
-user_trace_s1(Message) ->
+user_trace_s1(_Message) ->
     erlang:nif_error(nif_not_loaded).
 
 -spec user_trace_i4s4(iolist(),
@@ -176,8 +180,32 @@ p(I1, I2, I3, I4, S1, S2, S3, S4) when is_integer(I1), is_integer(I2), is_intege
       true | false | error | badarg.
 
 user_trace_int(I1, I2, I3, I4, S1, S2, S3, S4) ->
-    UTag = prim_file:get_dtrace_utag(),
-    user_trace_i4s4(UTag, I1, I2, I3, I4, S1, S2, S3, S4).
+    UTag = get_utag(),
+    try
+        user_trace_i4s4(UTag, I1, I2, I3, I4, S1, S2, S3, S4)
+    catch
+        error:nif_not_loaded ->
+            false
+    end.
+
+-spec put_utag(undefined | iolist()) -> ok.
+
+put_utag(undefined) ->
+    put_utag(<<>>);
+put_utag(T) when is_binary(T) ->
+    put(?DTRACE_UT_KEY, T),
+    ok;
+put_utag(T) when is_list(T) ->
+    put(?DTRACE_UT_KEY, list_to_binary(T)),
+    ok.
+
+get_utag() ->
+    case get(?DTRACE_UT_KEY) of
+        undefined ->
+            <<>>;
+        X ->
+            X
+    end.
 
 %% Scaffolding to write tedious code: quick brute force and not 100% correct.
 
diff --git a/lib/kernel/src/file.erl b/lib/kernel/src/file.erl
index a2e0d261ee..aecb9f7923 100644
--- a/lib/kernel/src/file.erl
+++ b/lib/kernel/src/file.erl
@@ -227,7 +227,7 @@ read_file_info(Name) ->
       Reason :: posix() | badarg.
 
 read_file_info(Name, Opts) when is_list(Opts) ->
-    check_and_call(read_file_info, [file_name(Name), Opts]).
+    check_and_call(read_file_info, [file_name(Name), Opts, get_dtrace_utag()]).
 
 -spec altname(Name :: name()) -> any().
 
@@ -249,7 +249,7 @@ read_link_info(Name) ->
       Reason :: posix() | badarg.
 
 read_link_info(Name, Opts) when is_list(Opts) ->
-    check_and_call(read_link_info, [file_name(Name),Opts]).
+    check_and_call(read_link_info, [file_name(Name),Opts, get_dtrace_utag()]).
 
 
 -spec read_link(Name) -> {ok, Filename} | {error, Reason} when
@@ -275,7 +275,7 @@ write_file_info(Name, Info = #file_info{}) ->
       Reason :: posix() | badarg.
 
 write_file_info(Name, Info = #file_info{}, Opts) when is_list(Opts) ->
-    check_and_call(write_file_info, [file_name(Name), Info, Opts]).
+    check_and_call(write_file_info, [file_name(Name), Info, Opts, get_dtrace_utag()]).
 
 -spec list_dir(Dir) -> {ok, Filenames} | {error, Reason} when
       Dir :: name(),
@@ -1504,4 +1504,4 @@ wait_file_reply(From, Ref) ->
     end.
 
 get_dtrace_utag() ->
-    prim_file:get_dtrace_utag().
+    dtrace:get_utag().
diff --git a/lib/kernel/src/file_server.erl b/lib/kernel/src/file_server.erl
index c917819508..82adc45795 100644
--- a/lib/kernel/src/file_server.erl
+++ b/lib/kernel/src/file_server.erl
@@ -146,7 +146,7 @@ handle_call({get_cwd, Name, DTraceUtag}, _From, Handle) ->
     {reply, ?PRIM_FILE:get_cwd(Handle, Name, DTraceUtag), Handle};
 
 handle_call({read_file_info, Name, DTraceUtag}, _From, Handle) ->
-    {reply, ?PRIM_FILE:read_file_info(Handle, Name, DTraceUtag), Handle};
+    {reply, ?PRIM_FILE:read_file_info(Handle, Name, [], DTraceUtag), Handle};
 handle_call({read_file_info, Name, Opts, DTraceUtag}, _From, Handle) ->
     {reply, ?PRIM_FILE:read_file_info(Handle, Name, Opts, DTraceUtag), Handle};
 
@@ -154,12 +154,12 @@ handle_call({altname, Name, DTraceUtag}, _From, Handle) ->
     {reply, ?PRIM_FILE:altname(Handle, Name, DTraceUtag), Handle};
 
 handle_call({write_file_info, Name, Info, DTraceUtag}, _From, Handle) ->
-    {reply, ?PRIM_FILE:write_file_info(Handle, Name, Info, DTraceUtag), Handle};
+    {reply, ?PRIM_FILE:write_file_info(Handle, Name, Info, [], DTraceUtag), Handle};
 handle_call({write_file_info, Name, Info, Opts, DTraceUtag}, _From, Handle) ->
     {reply, ?PRIM_FILE:write_file_info(Handle, Name, Info, Opts, DTraceUtag), Handle};
 
 handle_call({read_link_info, Name, DTraceUtag}, _From, Handle) ->
-    {reply, ?PRIM_FILE:read_link_info(Handle, Name, DTraceUtag), Handle};
+    {reply, ?PRIM_FILE:read_link_info(Handle, Name, [], DTraceUtag), Handle};
 handle_call({read_link_info, Name, Opts, DTraceUtag}, _From, Handle) ->
     {reply, ?PRIM_FILE:read_link_info(Handle, Name, Opts, DTraceUtag), Handle};