Raise a SIGCONT to the whole process group after receiving a SIGTTOU, so that pipelines can be resumed in the background (for example "pv /dev/zero | cat > /dev/null" can now be suspended and put into the background - if we do not send that signal then "cat" remains stopped, as mentioned in issue #56).
This commit is contained in:
Andrew Wood
@@ -1,6 +1,7 @@
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### UNRELEASED
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* i18n: complete set of German translations supplied by Hartmut Goebel ([#98](https://codeberg.org/a-j-wood/pv/pulls/98))
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* fix: resume stopped pipelines when running in the background (part of [#56](https://codeberg.org/a-j-wood/pv/issues/56))
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* fix: write UTC timestamps in debugging mode to avoid lockups in signal handlers
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* cleanup: removed TODO.md, since it's just an outdated copy of the issue tracker
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* cleanup: re-ordered structure members to reduce padding
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@@ -171,6 +171,7 @@ struct pvstate_s {
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volatile sig_atomic_t trigger_exit; /* whether we need to abort right now */
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volatile sig_atomic_t clear_tty_tostop_on_exit; /* whether to clear tty TOSTOP on exit */
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volatile sig_atomic_t suspend_stderr; /* whether writing to stderr is suspended */
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volatile sig_atomic_t skip_next_sigcont; /* whether to ignore the next SIGCONT */
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} flag;
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/*****************
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+80
-38
@@ -42,29 +42,38 @@ static void pv_sig_ensure_tty_tostop()
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if (NULL == pv_sig_state)
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return;
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/* Can't look at terminal flags if backgrounded. */
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if (1 == pv_sig_state->flag.suspend_stderr)
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return;
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if (0 != tcgetattr(STDERR_FILENO, &terminal_attributes)) {
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debug("%s: %s", "failed to read terminal attributes", strerror(errno));
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return;
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}
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/* Can't set terminal flags if backgrounded. */
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if (1 == pv_sig_state->flag.suspend_stderr)
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return;
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if (0 == (terminal_attributes.c_lflag & TOSTOP)) {
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terminal_attributes.c_lflag |= TOSTOP;
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if (0 == tcsetattr(STDERR_FILENO, TCSANOW, &terminal_attributes)) {
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pv_sig_state->flag.clear_tty_tostop_on_exit = 1;
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debug("%s", "set terminal TOSTOP attribute");
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#if HAVE_IPC
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/*
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* In "-c" mode with IPC, make all "pv -c" instances
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* aware that we set TOSTOP, so the last one can
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* clear it on exit.
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*/
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if (pv_sig_state->control.cursor && (NULL != pv_sig_state->cursor.shared)
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&& (!pv_sig_state->cursor.noipc)) {
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pv_sig_state->cursor.shared->tty_tostop_added = true;
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}
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#endif
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} else {
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debug("%s: %s", "failed to set terminal TOSTOP attribute", strerror(errno));
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}
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#if HAVE_IPC
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/*
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* In "-c" mode with IPC, make all "pv -c" instances aware
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* that we set TOSTOP, so the last one can clear it on exit.
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*/
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if (pv_sig_state->control.cursor && (NULL != pv_sig_state->cursor.shared)
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&& (!pv_sig_state->cursor.noipc)) {
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pv_sig_state->cursor.shared->tty_tostop_added = true;
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}
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#endif
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}
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}
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@@ -74,6 +83,11 @@ static void pv_sig_ensure_tty_tostop()
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* without messing up the terminal. On a subsequent SIGCONT we will try
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* writing to the terminal again, in case we get backgrounded and later get
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* foregrounded again.
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*
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* When we get backgrounded and cause a SIGTTOU, the rest of the pipeline
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* gets stopped too, so transfers involving pipelines need us to send a
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* SIGCONT to the rest of the process group here, otherwise backgrounding
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* stops transfers involving pipes.
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*/
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static void pv_sig_ttou( /*@unused@ */ __attribute__((unused))
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int s)
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@@ -84,6 +98,16 @@ static void pv_sig_ttou( /*@unused@ */ __attribute__((unused))
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if (1 != pv_sig_state->flag.suspend_stderr) {
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debug("%s", "SIGTTOU - suspending stderr");
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pv_sig_state->flag.suspend_stderr = 1;
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/* Also tell the SIGCONT handler to do nothing next time. */
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pv_sig_state->flag.skip_next_sigcont++;
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/* Raise an immediate SIGCONT to bring the rest of the pipeline back up. */
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/*@-unrecog@ *//* splint doesn't know about killpg() */
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if (0 != killpg(getpgrp(), SIGCONT)) {
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debug("%s: %s", "killpg", strerror(errno));
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}
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/*@+unrecog@ */
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} else {
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debug("%s", "SIGTTOU - but stderr was already suspended");
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}
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}
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@@ -118,6 +142,18 @@ static void pv_sig_cont( /*@unused@ */ __attribute__((unused))
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if (NULL == pv_sig_state)
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return;
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if (pv_sig_state->flag.skip_next_sigcont > 0) {
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debug("%s: %d", "SIGCONT received but ignored - current value of skip_next_sigcont",
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pv_sig_state->flag.skip_next_sigcont);
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pv_sig_state->flag.skip_next_sigcont--;
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return;
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} else if (pv_sig_state->flag.skip_next_sigcont < 0) {
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pv_sig_state->flag.skip_next_sigcont = 0;
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debug("%s", "skip_next_sigcont underrun cleared");
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}
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debug("%s: %d", "SIGCONT received - current value of suspend_stderr", pv_sig_state->flag.suspend_stderr);
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pv_sig_state->flag.terminal_resized = 1;
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/*
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@@ -143,18 +179,24 @@ static void pv_sig_cont( /*@unused@ */ __attribute__((unused))
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}
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/*
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* Try resuming our use of stderr, if we had suspended it.
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* Try resuming our use of stderr, if we had suspended it, but only
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* if we're now in the foreground.
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*/
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if (1 == pv_sig_state->flag.suspend_stderr) {
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debug("%s", "SIGCONT - resuming stderr");
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pv_sig_state->flag.suspend_stderr = 0;
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if (pv_in_foreground()) {
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debug("%s", "SIGCONT - resuming stderr");
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pv_sig_state->flag.suspend_stderr = 0;
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} else {
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debug("%s", "SIGCONT but still in background - not resuming stderr");
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}
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}
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pv_sig_ensure_tty_tostop();
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if (0 == pv_sig_state->flag.suspend_stderr) {
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pv_sig_ensure_tty_tostop();
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#ifdef HAVE_IPC
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pv_crs_needreinit(pv_sig_state);
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pv_crs_needreinit(pv_sig_state);
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#endif
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}
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}
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@@ -249,7 +291,7 @@ void pv_sig_init(pvstate_t state)
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/*
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* Note that wherever we use a "struct sigaction", we declare it
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* static and explicitly zero it before use, because it may contain
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* deeper structures (e.g. "sigset_t") which trigger splint
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* deeper structures (e.g. "sigset_t") which trigger splint
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* warnings about potential memory leaks.
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*/
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@@ -278,6 +320,7 @@ void pv_sig_init(pvstate_t state)
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* Handle SIGTTOU by continuing with output switched off, so that we
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* can be stopped and backgrounded without messing up the terminal.
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*/
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pv_sig_state->flag.skip_next_sigcont = 0;
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sa.sa_handler = pv_sig_ttou;
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(void) sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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@@ -393,7 +436,7 @@ void pv_sig_fini( /*@unused@ */ __attribute__((unused)) pvstate_t state)
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#endif
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(void) sigaction(SIGALRM, &(pv_sig_state->signal.old_sigalrm), NULL);
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need_to_clear_tostop = 1 == pv_sig_state->flag.clear_tty_tostop_on_exit ? true : false;
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need_to_clear_tostop = (1 == pv_sig_state->flag.clear_tty_tostop_on_exit) ? true : false;
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if (pv_sig_state->control.cursor) {
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#ifdef HAVE_IPC
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@@ -444,19 +487,17 @@ void pv_sig_fini( /*@unused@ */ __attribute__((unused)) pvstate_t state)
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*/
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void pv_sig_nopause(void)
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{
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static struct sigaction sa;
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sigset_t signal_set, signal_oldset;
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memset(&sa, 0, sizeof(sa));
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debug("%s", "blocking SIGTSTP, SIGCONT");
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sa.sa_handler = SIG_IGN;
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(void) sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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(void) sigaction(SIGTSTP, &sa, NULL);
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(void) sigemptyset(&signal_set);
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(void) sigaddset(&signal_set, SIGTSTP);
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(void) sigaddset(&signal_set, SIGCONT);
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sa.sa_handler = SIG_DFL;
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(void) sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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(void) sigaction(SIGCONT, &sa, NULL);
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if (0 != sigprocmask(SIG_BLOCK, &signal_set, &signal_oldset)) {
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debug("%s: %s", "failed to set signal mask", strerror(errno));
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}
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}
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@@ -465,19 +506,17 @@ void pv_sig_nopause(void)
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*/
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void pv_sig_allowpause(void)
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{
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static struct sigaction sa;
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sigset_t signal_set, signal_oldset;
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memset(&sa, 0, sizeof(sa));
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debug("%s", "unblocking SIGTSTP, SIGCONT");
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sa.sa_handler = pv_sig_tstp;
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(void) sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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(void) sigaction(SIGTSTP, &sa, NULL);
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(void) sigemptyset(&signal_set);
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(void) sigaddset(&signal_set, SIGTSTP);
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(void) sigaddset(&signal_set, SIGCONT);
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sa.sa_handler = pv_sig_cont;
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(void) sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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(void) sigaction(SIGCONT, &sa, NULL);
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if (0 != sigprocmask(SIG_UNBLOCK, &signal_set, &signal_oldset)) {
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debug("%s: %s", "failed to set signal mask", strerror(errno));
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}
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}
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@@ -501,6 +540,9 @@ void pv_sig_checkbg(void)
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if (0 == pv_sig_state->flag.suspend_stderr)
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return;
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if (!pv_in_foreground())
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return;
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debug("%s: %s", "pv_sig_checkbg", "attempting to resume stderr");
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pv_sig_state->flag.suspend_stderr = 0;
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Reference in New Issue
Block a user