From 30f05c1b6ccda73593bbf8490ac2f77804867111 Mon Sep 17 00:00:00 2001 From: Paul Tarjan Date: Thu, 5 Mar 2026 06:55:09 +0000 Subject: [PATCH] fsmonitor: close inherited file descriptors and detach in daemon When the fsmonitor daemon is spawned as a background process, it may inherit file descriptors from its parent that it does not need. In particular, when the test harness or a CI system captures output through pipes, the daemon can inherit duplicated pipe endpoints. If the daemon holds these open, the parent process never sees EOF and may appear to hang. Set close_fd_above_stderr on the child process at both daemon startup paths: the explicit "fsmonitor--daemon start" command and the implicit spawn triggered by fsmonitor-ipc when a client finds no running daemon. Also suppress stdout and stderr on the implicit spawn path to prevent the background daemon from writing to the client's terminal. Additionally, call setsid() when the daemon starts with --detach to create a new session and process group. This prevents the daemon from being part of the spawning shell's process group, which could cause the shell's "wait" to block until the daemon exits. Signed-off-by: Paul Tarjan Signed-off-by: Junio C Hamano --- builtin/fsmonitor--daemon.c | 16 ++++++++++++++-- fsmonitor-ipc.c | 3 +++ 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/builtin/fsmonitor--daemon.c b/builtin/fsmonitor--daemon.c index c8ec7b722e..b2a816dc3f 100644 --- a/builtin/fsmonitor--daemon.c +++ b/builtin/fsmonitor--daemon.c @@ -1439,7 +1439,7 @@ done: return err; } -static int try_to_run_foreground_daemon(int detach_console MAYBE_UNUSED) +static int try_to_run_foreground_daemon(int detach_console) { /* * Technically, we don't need to probe for an existing daemon @@ -1459,10 +1459,21 @@ static int try_to_run_foreground_daemon(int detach_console MAYBE_UNUSED) fflush(stderr); } + if (detach_console) { #ifdef GIT_WINDOWS_NATIVE - if (detach_console) FreeConsole(); +#else + /* + * Create a new session so that the daemon is detached + * from the parent's process group. This prevents + * shells with job control (e.g. bash with "set -m") + * from waiting on the daemon when they wait for a + * foreground command that implicitly spawned it. + */ + if (setsid() == -1) + warning_errno(_("setsid failed")); #endif + } return !!fsmonitor_run_daemon(); } @@ -1525,6 +1536,7 @@ static int try_to_start_background_daemon(void) cp.no_stdin = 1; cp.no_stdout = 1; cp.no_stderr = 1; + cp.close_fd_above_stderr = 1; sbgr = start_bg_command(&cp, bg_wait_cb, NULL, fsmonitor__start_timeout_sec); diff --git a/fsmonitor-ipc.c b/fsmonitor-ipc.c index f1b1631111..6112d13064 100644 --- a/fsmonitor-ipc.c +++ b/fsmonitor-ipc.c @@ -61,6 +61,9 @@ static int spawn_daemon(void) cmd.git_cmd = 1; cmd.no_stdin = 1; + cmd.no_stdout = 1; + cmd.no_stderr = 1; + cmd.close_fd_above_stderr = 1; cmd.trace2_child_class = "fsmonitor"; strvec_pushl(&cmd.args, "fsmonitor--daemon", "start", NULL);