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fsmonitor: close inherited file descriptors and detach in daemon

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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 <github@paulisageek.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Paul Tarjan
2026-03-05 06:55:09 +00:00
committed by Junio C Hamano
parent 89e7939fc9
commit 30f05c1b6c
2 changed files with 17 additions and 2 deletions
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16
builtin/fsmonitor--daemon.c
View File

@@ -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);

3
fsmonitor-ipc.c
View File

@@ -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);