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prim_tty: Use os:signal/2 to handle SIGCONT and SIGWINCH
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[Why]
Support for SIGCONT and SIGWINCH was added in previous commit to allow
any Erlang application to react to them. Unfortunately, setting handlers
for these two signals broke `prim_tty` which installed its own handlers
in `prim_tty_nif.c`.

[How]
This patch changes `prim_tty` to use `os:signal/2` along with its own
gen_event callbacu module to handle the two signals from the Erlang
code, like any other Erlang application.

The C code was removed because it is now unused.
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@dumbbell
dumbbell committed Oct 15, 2024
1 parent 2a253c2 commit 039d147
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Showing 6 changed files with 81 additions and 96 deletions.
75 changes: 0 additions & 75 deletions erts/emulator/nifs/common/prim_tty_nif.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -102,9 +102,6 @@ typedef struct {
ErlNifPid self;
ErlNifPid reader;
int tty; /* if the tty is initialized */
#ifndef __WIN32__
int signal[2]; /* Pipe used for signal (winch + cont) notifications */
#endif
#ifdef HAVE_TERMCAP
struct termios tty_smode;
struct termios tty_rmode;
Expand Down Expand Up @@ -142,14 +139,12 @@ static ERL_NIF_TERM tty_tgetnum_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM
static ERL_NIF_TERM tty_tgetflag_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
static ERL_NIF_TERM tty_tgetstr_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
static ERL_NIF_TERM tty_tgoto_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
static ERL_NIF_TERM tty_read_signal_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);

static ErlNifFunc nif_funcs[] = {
{"isatty", 1, isatty_nif},
{"tty_create", 0, tty_create_nif},
{"tty_init", 3, tty_init_nif},
{"tty_set", 1, tty_set_nif},
{"tty_read_signal", 2, tty_read_signal_nif},
{"setlocale", 1, setlocale_nif},
{"tty_select", 3, tty_select_nif},
{"tty_window_size", 1, tty_window_size_nif},
Expand Down Expand Up @@ -1015,60 +1010,6 @@ static ERL_NIF_TERM tty_window_size_nif(ErlNifEnv* env, int argc, const ERL_NIF_
));
}

#ifndef __WIN32__

static int tty_signal_fd = -1;

static RETSIGTYPE tty_cont(int sig)
{
if (tty_signal_fd != 1) {
while (write(tty_signal_fd, "c", 1) < 0 && errno == EINTR) { };
}
}


static RETSIGTYPE tty_winch(int sig)
{
if (tty_signal_fd != 1) {
while (write(tty_signal_fd, "w", 1) < 0 && errno == EINTR) { };
}
}

#endif

static ERL_NIF_TERM tty_read_signal_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) {
TTYResource *tty;
char buff[1];
ssize_t ret;
ERL_NIF_TERM res;
if (!enif_get_resource(env, argv[0], tty_rt, (void **)&tty))
return enif_make_badarg(env);
#ifndef __WIN32__
do {
ret = read(tty->signal[0], buff, 1);
} while (ret < 0 && errno == EAGAIN);

if (ret < 0) {
return make_errno_error(env, "read");
} else if (ret == 0) {
return make_error(env, enif_make_atom(env,"empty"));
}

enif_select(env, tty->signal[0], ERL_NIF_SELECT_READ, tty, NULL, argv[1]);

if (buff[0] == 'w') {
res = enif_make_atom(env, "winch");
} else if (buff[0] == 'c') {
res = enif_make_atom(env, "cont");
} else {
res = enif_make_string_len(env, buff, 1, ERL_NIF_LATIN1);
}
return enif_make_tuple2(env, atom_ok, res);
#else
return make_enotsup(env);
#endif
}

static ERL_NIF_TERM tty_select_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) {
TTYResource *tty;
#ifndef __WIN32__
Expand All @@ -1080,16 +1021,6 @@ static ERL_NIF_TERM tty_select_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM
return enif_make_badarg(env);

#ifndef __WIN32__
if (pipe(tty->signal) == -1) {
return make_errno_error(env, "pipe");
}
SET_NONBLOCKING(tty->signal[0]);
enif_select(env, tty->signal[0], ERL_NIF_SELECT_READ, tty, NULL, argv[1]);
tty_signal_fd = tty->signal[1];

sys_signal(SIGCONT, tty_cont);
sys_signal(SIGWINCH, tty_winch);

using_oldshell = 0;

enif_select(env, tty->ifd, ERL_NIF_SELECT_READ, tty, NULL, argv[2]);
Expand Down Expand Up @@ -1128,12 +1059,6 @@ static void tty_monitor_down(ErlNifEnv* caller_env, void* obj, ErlNifPid* pid, E
#endif
if (enif_compare_pids(pid, &tty->reader) == 0) {
enif_select(caller_env, tty->ifd, ERL_NIF_SELECT_STOP, tty, NULL, atom_undefined);
#ifndef __WIN32__
enif_select(caller_env, tty->signal[0], ERL_NIF_SELECT_STOP, tty, NULL, atom_undefined);
close(tty->signal[1]);
sys_signal(SIGCONT, SIG_DFL);
sys_signal(SIGWINCH, SIG_DFL);
#endif
}
}

Expand Down
1 change: 1 addition & 0 deletions lib/kernel/src/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,7 @@ MODULES = \
user_drv \
user_sup \
prim_tty \
prim_tty_sighandler \
raw_file_io \
raw_file_io_compressed \
raw_file_io_inflate \
Expand Down
1 change: 1 addition & 0 deletions lib/kernel/src/kernel.app.src
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,7 @@
user_drv,
user_sup,
prim_tty,
prim_tty_sighandler,
disk_log,
disk_log_1,
disk_log_server,
Expand Down
53 changes: 33 additions & 20 deletions lib/kernel/src/prim_tty.erl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -115,9 +115,9 @@
tty_select/3, tty_window_size/1, tty_encoding/1, write_nif/2, read_nif/2, isprint/1,
wcwidth/1, wcswidth/1,
sizeof_wchar/0, tgetent_nif/1, tgetnum_nif/1, tgetflag_nif/1, tgetstr_nif/1,
tgoto_nif/1, tgoto_nif/2, tgoto_nif/3, tty_read_signal/2]).
tgoto_nif/1, tgoto_nif/2, tgoto_nif/3]).

-export([reader_loop/6, writer_loop/2]).
-export([reader_loop/5, writer_loop/2]).

%% Exported in order to remove "unused function" warning
-export([sizeof_wchar/0, wcswidth/1, tgoto/1, tgoto/2, tgoto/3]).
Expand Down Expand Up @@ -320,6 +320,27 @@ init_term(State = #state{ tty = TTY, options = Options }) ->
WriterState
end,

%% `prim_tty' has signal handlers for SIGCONT and SIGWINCH.
%%
%% Historically, these signals were caught by `prim_tty_nif.c' and
%% forwarded to this process.
%%
%% After SIGCONT and SIGWINCH support was added, this module uses a
%% gen_event handler in `prim_tty_sighandler'.
_ = gen_event:delete_handler(
erl_signal_server, prim_tty_sighandler,
undefined),
case ReaderState#state.reader of
{_ReaderPid, ReaderRef} ->
ok = gen_event:add_handler(
erl_signal_server, prim_tty_sighandler,
#{parent => self(), reader => ReaderRef}),
ok = os:set_signal(sigcont, handle),
ok = os:set_signal(sigwinch, handle);
undefined ->
ok
end,

update_geometry(ReaderState).

-spec reinit(state(), options()) -> state().
Expand Down Expand Up @@ -497,34 +518,29 @@ call(Pid, Msg) ->
reader([TTY, Encoding, Parent]) ->
register(user_drv_reader, self()),
ReaderRef = make_ref(),
SignalRef = make_ref(),

ok = tty_select(TTY, SignalRef, ReaderRef),
ok = tty_select(TTY, undefined, ReaderRef),
proc_lib:init_ack({ok, {self(), ReaderRef}}),
FromEnc = case tty_encoding(TTY) of
utf8 -> Encoding;
Else -> Else
end,
reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, <<>>).
reader_loop(TTY, Parent, ReaderRef, FromEnc, <<>>).

reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc) ->
reader_loop(TTY, Parent, ReaderRef, FromEnc, Acc) ->
receive
{DisableAlias, disable} ->
DisableAlias ! {DisableAlias, ok},
receive
{EnableAlias, enable} ->
EnableAlias ! {EnableAlias, ok},
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc)
?MODULE:reader_loop(TTY, Parent, ReaderRef, FromEnc, Acc)
end;
{select, TTY, SignalRef, ready_input} ->
{ok, Signal} = tty_read_signal(TTY, SignalRef),
Parent ! {ReaderRef,{signal,Signal}},
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc);
{set_unicode_state, _} when FromEnc =:= {utf16, little} ->
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc);
?MODULE:reader_loop(TTY, Parent, ReaderRef, FromEnc, Acc);
{set_unicode_state, Bool} ->
NewFromEnc = if Bool -> utf8; not Bool -> latin1 end,
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, NewFromEnc, Acc);
?MODULE:reader_loop(TTY, Parent, ReaderRef, NewFromEnc, Acc);
{_Alias, stop} ->
ok;
{select, TTY, ReaderRef, ready_input} ->
Expand All @@ -538,10 +554,10 @@ reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc) ->
%% Windows when we change from "noshell" to "newshell".
%% When it happens we need to re-read the tty_encoding as
%% it has changed.
reader_loop(TTY, Parent, SignalRef, ReaderRef, tty_encoding(TTY), Acc);
reader_loop(TTY, Parent, ReaderRef, tty_encoding(TTY), Acc);
{ok, <<>>} ->
%% EAGAIN or EINTR
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc);
?MODULE:reader_loop(TTY, Parent, ReaderRef, FromEnc, Acc);
{ok, UtfXBytes} ->

%% read_nif may have blocked for a long time, so we check if
Expand Down Expand Up @@ -570,7 +586,7 @@ reader_loop(TTY, Parent, SignalRef, ReaderRef, FromEnc, Acc) ->
{B, <<>>, UpdatedFromEnc}
end,
Parent ! {ReaderRef, {data, Bytes}},
?MODULE:reader_loop(TTY, Parent, SignalRef, ReaderRef, NewFromEnc, NewAcc)
?MODULE:reader_loop(TTY, Parent, ReaderRef, NewFromEnc, NewAcc)
end
end.

Expand Down Expand Up @@ -1403,7 +1419,7 @@ tty_set(_TTY) ->
erlang:nif_error(undef).
setlocale(_TTY) ->
erlang:nif_error(undef).
tty_select(_TTY, _SignalRef, _ReadRef) ->
tty_select(_TTY, undefined, _ReadRef) ->
erlang:nif_error(undef).
tty_encoding(_TTY) ->
erlang:nif_error(undef).
Expand Down Expand Up @@ -1454,6 +1470,3 @@ tgoto_nif(_Ent, _Arg) ->
erlang:nif_error(undef).
tgoto_nif(_Ent, _Arg1, _Arg2) ->
erlang:nif_error(undef).
tty_read_signal(_TTY, _Ref) ->
erlang:nif_error(undef).

45 changes: 45 additions & 0 deletions lib/kernel/src/prim_tty_sighandler.erl
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2024. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
-module(prim_tty_sighandler).
-moduledoc false.

-behaviour(gen_event).

-export([init/1, handle_event/2, handle_call/2, code_change/3]).

init(#{parent := _, reader := _} = State) ->
{ok, State}.

handle_event(Signal, #{parent := Parent, reader := ReaderRef} = State)
when Signal =:= sigcont orelse Signal =:= sigwinch ->
ShortSignal = case Signal of
sigcont -> cont;
sigwinch -> winch
end,
Parent ! {ReaderRef, {signal, ShortSignal}},
{ok, State};
handle_event(_Signal, State) ->
%% Other signals are ignored by `prim_tty'.
{ok, State}.

handle_call(_Request, State) ->
{ok, ok, State}.

code_change(_OldVsn, State, _Extra) ->
{ok, State}.
2 changes: 1 addition & 1 deletion lib/kernel/test/tty.cover
View file
Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
%% -*- erlang -*-
{incl_mods,[prim_tty, user_drv, group, shell, edlin, edlin_expand, io_lib]}.
{incl_mods,[prim_tty, prim_tty_sighandler, user_drv, group, shell, edlin, edlin_expand, io_lib]}.

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