From fdb1322651a41a4e754bfac23513c0fa32dc1db8 Mon Sep 17 00:00:00 2001 From: Jeff Hostetler Date: Mon, 20 Sep 2021 15:36:17 +0000 Subject: run-command: create start_bg_command Create a variation of `run_command()` and `start_command()` to launch a command into the background and optionally wait for it to become "ready" before returning. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano --- run-command.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) (limited to 'run-command.c') diff --git a/run-command.c b/run-command.c index 3e4e082e94..76bbef9d96 100644 --- a/run-command.c +++ b/run-command.c @@ -1901,3 +1901,132 @@ void prepare_other_repo_env(struct strvec *env_array, const char *new_git_dir) } strvec_pushf(env_array, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir); } + +enum start_bg_result start_bg_command(struct child_process *cmd, + start_bg_wait_cb *wait_cb, + void *cb_data, + unsigned int timeout_sec) +{ + enum start_bg_result sbgr = SBGR_ERROR; + int ret; + int wait_status; + pid_t pid_seen; + time_t time_limit; + + /* + * We do not allow clean-on-exit because the child process + * should persist in the background and possibly/probably + * after this process exits. So we don't want to kill the + * child during our atexit routine. + */ + if (cmd->clean_on_exit) + BUG("start_bg_command() does not allow non-zero clean_on_exit"); + + if (!cmd->trace2_child_class) + cmd->trace2_child_class = "background"; + + ret = start_command(cmd); + if (ret) { + /* + * We assume that if `start_command()` fails, we + * either get a complete `trace2_child_start() / + * trace2_child_exit()` pair or it fails before the + * `trace2_child_start()` is emitted, so we do not + * need to worry about it here. + * + * We also assume that `start_command()` does not add + * us to the cleanup list. And that it calls + * calls `child_process_clear()`. + */ + sbgr = SBGR_ERROR; + goto done; + } + + time(&time_limit); + time_limit += timeout_sec; + +wait: + pid_seen = waitpid(cmd->pid, &wait_status, WNOHANG); + + if (!pid_seen) { + /* + * The child is currently running. Ask the callback + * if the child is ready to do work or whether we + * should keep waiting for it to boot up. + */ + ret = (*wait_cb)(cmd, cb_data); + if (!ret) { + /* + * The child is running and "ready". + */ + trace2_child_ready(cmd, "ready"); + sbgr = SBGR_READY; + goto done; + } else if (ret > 0) { + /* + * The callback said to give it more time to boot up + * (subject to our timeout limit). + */ + time_t now; + + time(&now); + if (now < time_limit) + goto wait; + + /* + * Our timeout has expired. We don't try to + * kill the child, but rather let it continue + * (hopefully) trying to startup. + */ + trace2_child_ready(cmd, "timeout"); + sbgr = SBGR_TIMEOUT; + goto done; + } else { + /* + * The cb gave up on this child. It is still running, + * but our cb got an error trying to probe it. + */ + trace2_child_ready(cmd, "error"); + sbgr = SBGR_CB_ERROR; + goto done; + } + } + + else if (pid_seen == cmd->pid) { + int child_code = -1; + + /* + * The child started, but exited or was terminated + * before becoming "ready". + * + * We try to match the behavior of `wait_or_whine()` + * WRT the handling of WIFSIGNALED() and WIFEXITED() + * and convert the child's status to a return code for + * tracing purposes and emit the `trace2_child_exit()` + * event. + * + * We do not want the wait_or_whine() error message + * because we will be called by client-side library + * routines. + */ + if (WIFEXITED(wait_status)) + child_code = WEXITSTATUS(wait_status); + else if (WIFSIGNALED(wait_status)) + child_code = WTERMSIG(wait_status) + 128; + trace2_child_exit(cmd, child_code); + + sbgr = SBGR_DIED; + goto done; + } + + else if (pid_seen < 0 && errno == EINTR) + goto wait; + + trace2_child_exit(cmd, -1); + sbgr = SBGR_ERROR; + +done: + child_process_clear(cmd); + invalidate_lstat_cache(); + return sbgr; +} -- cgit v1.2.3