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authorBjörn Gustavsson <bjorn@erlang.org>2014-03-07 10:41:32 +0100
committerBjörn Gustavsson <bjorn@erlang.org>2014-03-20 13:10:36 +0100
commit9327904dcbf2708823c05baa7532783fb0214792 (patch)
treed5f157e885b0ccdbe63f95173df72425f1a9d468 /erts
parent544fb141916d8676bc763318074e4d0783414af1 (diff)
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Teach the call_time trace to notice when the trace dies (non-SMP system)
The call_time trace is a special kind of tracing that requires a tracer process just like ordinary call trace, but it never actually sends anything to the tracer. It merely use the existence of a trace process (and call trace flags) as an indication that call_time tracing is active for the process. If the tracer dies in a non-SMP run-time system, processes with call_time tracing would not notice that the tracer had died. Furthermore, if the set_on_spawn flag was active, the dead tracer could be propagaged to newly spawned processes. Before accumulating trace information in a non-SMP system, always validate the tracer process. (In an SMP system, a reference to a dead tracer will be cleared away each time a process is scheduled.) While we could put all of the new code beam_bp.c, we have chosen to make a function call from beam_bp.c to a function in erl_trace.c for clarity's sake and to ease further maintenance. In the future, we might want to handle tracing in more similar ways in the SMP and non-SMP system.
Diffstat (limited to 'erts')
-rw-r--r--erts/emulator/beam/beam_bp.c5
-rw-r--r--erts/emulator/beam/erl_trace.c19
-rw-r--r--erts/emulator/beam/erl_trace.h1
-rw-r--r--erts/emulator/test/trace_call_time_SUITE.erl96
4 files changed, 115 insertions, 6 deletions
diff --git a/erts/emulator/beam/beam_bp.c b/erts/emulator/beam/beam_bp.c
index 49a34ab4ad..4e711c89e0 100644
--- a/erts/emulator/beam/beam_bp.c
+++ b/erts/emulator/beam/beam_bp.c
@@ -642,7 +642,7 @@ erts_generic_breakpoint(Process* c_p, BeamInstr* I, Eterm* reg)
erts_smp_atomic_inc_nob(&bp->count->acount);
}
- if (bp_flags & ERTS_BPF_TIME_TRACE_ACTIVE) {
+ if (bp_flags & ERTS_BPF_TIME_TRACE_ACTIVE && erts_is_tracer_proc_valid(c_p)) {
Eterm w;
erts_trace_time_call(c_p, I, bp->time);
w = (BeamInstr) *c_p->cp;
@@ -730,7 +730,8 @@ erts_bif_trace(int bif_index, Process* p, Eterm* args, BeamInstr* I)
}
}
if (bp_flags & ERTS_BPF_TIME_TRACE_ACTIVE &&
- IS_TRACED_FL(p, F_TRACE_CALLS)) {
+ IS_TRACED_FL(p, F_TRACE_CALLS) &&
+ erts_is_tracer_proc_valid(p)) {
BeamInstr *pc = (BeamInstr *)ep->code+3;
erts_trace_time_call(p, pc, bp->time);
}
diff --git a/erts/emulator/beam/erl_trace.c b/erts/emulator/beam/erl_trace.c
index 6978a5f11a..305058ceff 100644
--- a/erts/emulator/beam/erl_trace.c
+++ b/erts/emulator/beam/erl_trace.c
@@ -151,6 +151,11 @@ do { \
message dispatcher thread takes care of that). */
#define ERTS_GET_TRACER_REF(RES, TPID, TRACEE_FLGS) \
do { (RES) = (TPID); } while(0)
+int
+erts_is_tracer_proc_valid(Process* p)
+{
+ return 1;
+}
#else
#define ERTS_NULL_TRACER_REF NULL
#define ERTS_TRACER_REF_TYPE Process *
@@ -163,6 +168,20 @@ do { \
return; \
} \
} while (0)
+int
+erts_is_tracer_proc_valid(Process* p)
+{
+ Process* tracer;
+
+ tracer = erts_proc_lookup(ERTS_TRACER_PROC(p));
+ if (tracer && ERTS_TRACE_FLAGS(tracer) & F_TRACER) {
+ return 1;
+ } else {
+ ERTS_TRACER_PROC(p) = NIL;
+ ERTS_TRACE_FLAGS(p) = ~TRACEE_FLAGS;
+ return 0;
+ }
+}
#endif
static Uint active_sched;
diff --git a/erts/emulator/beam/erl_trace.h b/erts/emulator/beam/erl_trace.h
index 853c6cb0d8..4f2c70d6e7 100644
--- a/erts/emulator/beam/erl_trace.h
+++ b/erts/emulator/beam/erl_trace.h
@@ -39,6 +39,7 @@ void erts_change_default_tracing(int setflags, Uint *flagsp, Eterm *tracerp);
void erts_get_default_tracing(Uint *flagsp, Eterm *tracerp);
void erts_set_system_monitor(Eterm monitor);
Eterm erts_get_system_monitor(void);
+int erts_is_tracer_proc_valid(Process* p);
#ifdef ERTS_SMP
void erts_check_my_tracer_proc(Process *);
diff --git a/erts/emulator/test/trace_call_time_SUITE.erl b/erts/emulator/test/trace_call_time_SUITE.erl
index 5dfa87bbee..3036d2957b 100644
--- a/erts/emulator/test/trace_call_time_SUITE.erl
+++ b/erts/emulator/test/trace_call_time_SUITE.erl
@@ -33,7 +33,7 @@
%% Exported end user tests
-export([seq/3, seq_r/3]).
--export([loaded/1, a_function/1, a_called_function/1, dec/1, nif_dec/1]).
+-export([loaded/1, a_function/1, a_called_function/1, dec/1, nif_dec/1, dead_tracer/1]).
-define(US_ERROR, 10000).
-define(R_ERROR, 0.8).
@@ -89,7 +89,7 @@ all() ->
true -> [not_run];
false ->
[basic, on_and_off, info, pause_and_restart, scheduling,
- combo, bif, nif, called_function]
+ combo, bif, nif, called_function, dead_tracer]
end.
groups() ->
@@ -470,6 +470,92 @@ called_function(Config) when is_list(Config) ->
?line P = erlang:trace_pattern({'_','_','_'}, false, [call_time]),
ok.
+%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+dead_tracer(Config) when is_list(Config) ->
+ Self = self(),
+ FirstTracer = tracer(),
+ StartTracing = fun() -> turn_on_tracing(Self) end,
+ tell_tracer(FirstTracer, StartTracing),
+ [1,2,3,4,5,6,7,8] = seq(1, 8, fun(I) -> I + 1 end),
+ Ref = erlang:monitor(process, FirstTracer),
+ FirstTracer ! quit,
+ receive
+ {'DOWN',Ref,process,FirstTracer,normal} ->
+ ok
+ end,
+ erlang:yield(),
+
+ %% Collect and check that we only get call_time info for the current process.
+ Info1 = collect_all_info(),
+ [] = other_than_self(Info1),
+ io:format("~p\n", [Info1]),
+
+ %% Note that we have not turned off tracing for the current process,
+ %% but that the tracer has terminated. No more call_time information should be recorded.
+ [1,2,3] = seq(1, 3, fun(I) -> I + 1 end),
+ [] = collect_all_info(),
+
+ %% When we start a second tracer process, that tracer process must
+ %% not inherit the tracing flags and the dead tracer (even though
+ %% we used set_on_spawn).
+ SecondTracer = tracer(),
+ tell_tracer(SecondTracer, StartTracing),
+ Seq20 = lists:seq(1, 20),
+ Seq20 = seq(1, 20, fun(I) -> I + 1 end),
+ Info2 = collect_all_info(),
+ io:format("~p\n", [Info2]),
+ [] = other_than_self(Info2),
+ SecondTracer ! quit,
+
+ ok.
+
+other_than_self(Info) ->
+ [{Pid,MFA} || {MFA,[{Pid,_,_,_}]} <- Info,
+ Pid =/= self()].
+
+tell_tracer(Tracer, Fun) ->
+ Tracer ! {execute,self(),Fun},
+ receive
+ {Tracer,executed} ->
+ ok
+ end.
+
+tracer() ->
+ spawn_link(fun Loop() ->
+ receive
+ quit ->
+ ok;
+ {execute,From,Fun} ->
+ Fun(),
+ From ! {self(),executed},
+ Loop()
+ end
+ end).
+
+turn_on_tracing(Pid) ->
+ _ = erlang:trace(Pid, true, [call,set_on_spawn]),
+ _ = erlang:trace_pattern({?MODULE,'_','_'}, true, [call_time]),
+ _ = now(),
+ ok.
+
+collect_all_info() ->
+ collect_all_info([{?MODULE,F,A} || {F,A} <- module_info(functions)] ++
+ erlang:system_info(snifs)).
+
+collect_all_info([MFA|T]) ->
+ CallTime = erlang:trace_info(MFA, call_time),
+ erlang:trace_pattern(MFA, restart, [call_time]),
+ case CallTime of
+ {call_time,false} ->
+ collect_all_info(T);
+ {call_time,[]} ->
+ collect_all_info(T);
+ {call_time,[_|_]=List} ->
+ [{MFA,List}|collect_all_info(T)]
+ end;
+collect_all_info([]) -> [].
+
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% The Tests
%%%
@@ -478,7 +564,6 @@ called_function(Config) when is_list(Config) ->
%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Local helpers
-
load_nif(Config) ->
?line Path = ?config(data_dir, Config),
?line ok = erlang:load_nif(filename:join(Path,"trace_nif"), 0).
@@ -602,8 +687,11 @@ collect(A, Ref) ->
end.
setup() ->
+ setup([]).
+
+setup(Opts) ->
Pid = spawn_link(fun() -> loop() end),
- ?line 1 = erlang:trace(Pid, true, [call]),
+ 1 = erlang:trace(Pid, true, [call|Opts]),
Pid.
execute(Pids, Mfa) when is_list(Pids) ->