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Factor out some of the crazy logic in reader_interactive_init

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ridiculousfish 2020-01-31 11:11:03 -08:00
parent 8d8bcb7d8a
commit 1101cff566
1 changed files with 80 additions and 67 deletions
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147
src/reader.cpp
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@ -1683,84 +1683,97 @@ static bool check_for_orphaned_process(unsigned long loop_count, pid_t shell_pgi
return we_think_we_are_orphaned;
}
/// Initialize data for interactive use.
static void reader_interactive_init(parser_t &parser) {
// See if we are running interactively.
pid_t shell_pgid;
init_input();
shell_pgid = getpgrp();
// This should enable job control on fish, even if our parent process did not enable it for us.
// Ensure that fish owns the terminal, possibly waiting. If we cannot acquire the terminal, then
// report an error and exit.
static void acquire_tty_or_exit(pid_t shell_pgid) {
ASSERT_IS_MAIN_THREAD();
// Check if we are in control of the terminal, so that we don't do semi-expensive things like
// reset signal handlers unless we really have to, which we often don't.
if (tcgetpgrp(STDIN_FILENO) != shell_pgid) {
// Bummer, we are not in control of the terminal. Stop until parent has given us control of
// it.
//
// In theory, reseting signal handlers could cause us to miss signal deliveries. In
// practice, this code should only be run during startup, when we're not waiting for any
// signals.
signal_reset_handlers();
// Common case.
if (tcgetpgrp(STDIN_FILENO) == shell_pgid) {
return;
}
// Ok, signal handlers are taken out of the picture. Stop ourself in a loop until we are in
// control of the terminal. However, the call to signal(SIGTTIN) may silently not do
// anything if we are orphaned.
//
// As far as I can tell there's no really good way to detect that we are orphaned. One way
// is to just detect if the group leader exited, via kill(shell_pgid, 0). Another
// possibility is that read() from the tty fails with EIO - this is more reliable but it's
// harder, because it may succeed or block. So we loop for a while, trying those strategies.
// Eventually we just give up and assume we're orphaend.
for (unsigned long loop_count = 0;; loop_count++) {
pid_t owner = tcgetpgrp(STDIN_FILENO);
// 0 is a valid return code from `tcgetpgrp()` under at least FreeBSD and testing
// indicates that a subsequent call to `tcsetpgrp()` will succeed. 0 is the
// pid of the top-level kernel process, so I'm not sure if this means ownership
// of the terminal has gone back to the kernel (i.e. it's not owned) or if it is
// just an "invalid" pid for all intents and purposes.
if (owner == 0) {
tcsetpgrp(STDIN_FILENO, shell_pgid);
// Since we expect the above to work, call `tcgetpgrp()` immediately to
// avoid a second pass through this loop.
owner = tcgetpgrp(STDIN_FILENO);
// Bummer, we are not in control of the terminal. Stop until parent has given us control of
// it.
//
// In theory, reseting signal handlers could cause us to miss signal deliveries. In
// practice, this code should only be run during startup, when we're not waiting for any
// signals.
signal_reset_handlers();
cleanup_t restore_sigs([] { signal_set_handlers(true); });
// Ok, signal handlers are taken out of the picture. Stop ourself in a loop until we are in
// control of the terminal. However, the call to signal(SIGTTIN) may silently not do
// anything if we are orphaned.
//
// As far as I can tell there's no really good way to detect that we are orphaned. One way
// is to just detect if the group leader exited, via kill(shell_pgid, 0). Another
// possibility is that read() from the tty fails with EIO - this is more reliable but it's
// harder, because it may succeed or block. So we loop for a while, trying those strategies.
// Eventually we just give up and assume we're orphaend.
for (unsigned loop_count = 0;; loop_count++) {
pid_t owner = tcgetpgrp(STDIN_FILENO);
// 0 is a valid return code from `tcgetpgrp()` under at least FreeBSD and testing
// indicates that a subsequent call to `tcsetpgrp()` will succeed. 0 is the
// pid of the top-level kernel process, so I'm not sure if this means ownership
// of the terminal has gone back to the kernel (i.e. it's not owned) or if it is
// just an "invalid" pid for all intents and purposes.
if (owner == 0) {
tcsetpgrp(STDIN_FILENO, shell_pgid);
// Since we expect the above to work, call `tcgetpgrp()` immediately to
// avoid a second pass through this loop.
owner = tcgetpgrp(STDIN_FILENO);
}
if (owner == -1 && errno == ENOTTY) {
if (session_interactivity() == session_interactivity_t::not_interactive) {
// It's OK if we're not able to take control of the terminal. We handle
// the fallout from this in a few other places.
break;
}
if (owner == -1 && errno == ENOTTY) {
if (session_interactivity() == session_interactivity_t::not_interactive) {
// It's OK if we're not able to take control of the terminal. We handle
// the fallout from this in a few other places.
break;
}
// No TTY, cannot be interactive?
redirect_tty_output();
FLOGF(warning, _(L"No TTY for interactive shell (tcgetpgrp failed)"));
wperror(L"setpgid");
// No TTY, cannot be interactive?
redirect_tty_output();
FLOGF(warning, _(L"No TTY for interactive shell (tcgetpgrp failed)"));
wperror(L"setpgid");
exit_without_destructors(1);
}
if (owner == shell_pgid) {
break; // success
} else {
if (check_for_orphaned_process(loop_count, shell_pgid)) {
// We're orphaned, so we just die. Another sad statistic.
const wchar_t *fmt =
_(L"I appear to be an orphaned process, so I am quitting politely. "
L"My pid is %d.");
FLOGF(warning, fmt, (int)getpid());
exit_without_destructors(1);
}
if (owner == shell_pgid) {
break; // success
} else {
if (check_for_orphaned_process(loop_count, shell_pgid)) {
// We're orphaned, so we just die. Another sad statistic.
const wchar_t *fmt =
_(L"I appear to be an orphaned process, so I am quitting politely. "
L"My pid is %d.");
FLOGF(warning, fmt, (int)getpid());
exit_without_destructors(1);
}
// Try stopping us.
int ret = killpg(shell_pgid, SIGTTIN);
if (ret < 0) {
wperror(L"killpg(shell_pgid, SIGTTIN)");
exit_without_destructors(1);
}
// Try stopping us.
int ret = killpg(shell_pgid, SIGTTIN);
if (ret < 0) {
wperror(L"killpg(shell_pgid, SIGTTIN)");
exit_without_destructors(1);
}
}
signal_set_handlers(parser.is_interactive());
}
}
/// Initialize data for interactive use.
static void reader_interactive_init(parser_t &parser) {
ASSERT_IS_MAIN_THREAD();
pid_t shell_pgid = getpgrp();
// Set up key bindings.
init_input();
// Ensure interactive signal handling is enabled.
signal_set_handlers_once(true);
// Wait until we own the terminal.
acquire_tty_or_exit(shell_pgid);
// It shouldn't be necessary to place fish in its own process group and force control
// of the terminal, but that works around fish being started with an invalid pgroup,