93ae7464e
Denys Vlasenko
2023-01-30
Subject
hush: restore SIGHUP handling, this time explain why we do what we do
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shell/hush.c+28 -20
| @@ -1829,12 +1829,13 @@ static void restore_G_args(save_arg_t *sv, char **argv) | |
| * SIGQUIT: ignore | |
| * SIGTERM (interactive): ignore | |
| * SIGHUP (interactive): | |
| - | * send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit |
| - | //HUP: we don't need to do this, kernel does this for us |
| - | //HUP: ("orphaned process group" handling according to POSIX). |
| - | //HUP: We still have a SIGHUP handler, just to have tty pgrp restored |
| - | //HUP: (otherwise e.g. Midnight Commander backgrounds when hush |
| - | //HUP: started from it gets killed by SIGHUP). |
| + | * Send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit. |
| + | * Kernel would do this for us ("orphaned process group" handling |
| + | * according to POSIX) if we are a session leader and thus our death |
| + | * frees the controlling tty, but to be bash-compatible, we also do it |
| + | * for every interactive shell's death by SIGHUP. |
| + | * (Also, we need to restore tty pgrp, otherwise e.g. Midnight Commander |
| + | * backgrounds when hush started from it gets killed by SIGHUP). |
| * SIGTTIN, SIGTTOU, SIGTSTP (if job control is on): ignore | |
| * Note that ^Z is handled not by trapping SIGTSTP, but by seeing | |
| * that all pipe members are stopped. Try this in bash: | |
| @@ -2183,20 +2184,27 @@ static int check_and_run_traps(void) | |
| break; | |
| #if ENABLE_HUSH_JOB | |
| case SIGHUP: { | |
| - | //HUP//TODO: why are we doing this? ash and dash don't do this, |
| - | //HUP//they have no handler for SIGHUP at all, |
| - | //HUP//they rely on kernel to send SIGHUP+SIGCONT to orphaned process groups |
| - | //HUP struct pipe *job; |
| - | //HUP debug_printf_exec("%s: sig:%d default SIGHUP handler\n", __func__, sig); |
| - | //HUP /* bash is observed to signal whole process groups, |
| - | //HUP * not individual processes */ |
| - | //HUP for (job = G.job_list; job; job = job->next) { |
| - | //HUP if (job->pgrp <= 0) |
| - | //HUP continue; |
| - | //HUP debug_printf_exec("HUPing pgrp %d\n", job->pgrp); |
| - | //HUP if (kill(- job->pgrp, SIGHUP) == 0) |
| - | //HUP kill(- job->pgrp, SIGCONT); |
| - | //HUP } |
| + | /* if (G_interactive_fd) - no need to check, the handler |
| + | * is only installed if we *are* interactive */ |
| + | { |
| + | /* bash compat: "Before exiting, an interactive |
| + | * shell resends the SIGHUP to all jobs, running |
| + | * or stopped. Stopped jobs are sent SIGCONT |
| + | * to ensure that they receive the SIGHUP." |
| + | */ |
| + | struct pipe *job; |
| + | debug_printf_exec("%s: sig:%d default SIGHUP handler\n", __func__, sig); |
| + | /* bash is observed to signal whole process groups, |
| + | * not individual processes */ |
| + | for (job = G.job_list; job; job = job->next) { |
| + | if (job->pgrp <= 0) |
| + | continue; |
| + | debug_printf_exec("HUPing pgrp %d\n", job->pgrp); |
| + | if (kill(- job->pgrp, SIGHUP) == 0) |
| + | kill(- job->pgrp, SIGCONT); |
| + | } |
| + | } |
| + | /* this restores tty pgrp, then kills us with SIGHUP */ |
| sigexit(SIGHUP); | |
| } | |
| #endif | |