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[PATCH v3] qemu-storage-daemon: add --pidfile option
From: |
Stefan Hajnoczi |
Subject: |
[PATCH v3] qemu-storage-daemon: add --pidfile option |
Date: |
Tue, 2 Mar 2021 14:27:46 +0000 |
Daemons often have a --pidfile option where the pid is written to a file
so that scripts can stop the daemon by sending a signal.
The pid file also acts as a lock to prevent multiple instances of the
daemon from launching for a given pid file.
QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the
--pidfile option. Add it to qemu-storage-daemon too.
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
v3:
* Add --pidfile help output [Kevin]
docs/tools/qemu-storage-daemon.rst | 14 +++++++++++
storage-daemon/qemu-storage-daemon.c | 36 ++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/docs/tools/qemu-storage-daemon.rst
b/docs/tools/qemu-storage-daemon.rst
index f63627eaf6..3d9704d835 100644
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -118,6 +118,20 @@ Standard options:
List object properties with ``<type>,help``. See the :manpage:`qemu(1)`
manual page for a description of the object properties.
+.. option:: --pidfile PATH
+
+ is the path to a file where the daemon writes its pid. This allows scripts to
+ stop the daemon by sending a signal::
+
+ $ kill -SIGTERM $(<path/to/qsd.pid)
+
+ A file lock is applied to the file so only one instance of the daemon can run
+ with a given pid file path. The daemon unlinks its pid file when terminating.
+
+ The pid file is written after chardevs, exports, and NBD servers have been
+ created but before accepting connections. The daemon has started successfully
+ when the pid file is written and clients may begin connecting.
+
Examples
--------
Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute
diff --git a/storage-daemon/qemu-storage-daemon.c
b/storage-daemon/qemu-storage-daemon.c
index 9021a46b3a..4672145df5 100644
--- a/storage-daemon/qemu-storage-daemon.c
+++ b/storage-daemon/qemu-storage-daemon.c
@@ -59,6 +59,7 @@
#include "sysemu/runstate.h"
#include "trace/control.h"
+static const char *pid_file;
static volatile bool exit_requested = false;
void qemu_system_killed(int signal, pid_t pid)
@@ -115,6 +116,8 @@ static void help(void)
" See the qemu(1) man page for documentation of the\n"
" objects that can be added.\n"
"\n"
+" --pidfile <path> write process ID to a file after startup\n"
+"\n"
QEMU_HELP_BOTTOM "\n",
error_get_progname());
}
@@ -126,6 +129,7 @@ enum {
OPTION_MONITOR,
OPTION_NBD_SERVER,
OPTION_OBJECT,
+ OPTION_PIDFILE,
};
extern QemuOptsList qemu_chardev_opts;
@@ -164,6 +168,7 @@ static void process_options(int argc, char *argv[])
{"monitor", required_argument, NULL, OPTION_MONITOR},
{"nbd-server", required_argument, NULL, OPTION_NBD_SERVER},
{"object", required_argument, NULL, OPTION_OBJECT},
+ {"pidfile", required_argument, NULL, OPTION_PIDFILE},
{"trace", required_argument, NULL, 'T'},
{"version", no_argument, NULL, 'V'},
{0, 0, 0, 0}
@@ -275,6 +280,9 @@ static void process_options(int argc, char *argv[])
qobject_unref(args);
break;
}
+ case OPTION_PIDFILE:
+ pid_file = optarg;
+ break;
default:
g_assert_not_reached();
}
@@ -285,6 +293,27 @@ static void process_options(int argc, char *argv[])
}
}
+static void pid_file_cleanup(void)
+{
+ unlink(pid_file);
+}
+
+static void pid_file_init(void)
+{
+ Error *err = NULL;
+
+ if (!pid_file) {
+ return;
+ }
+
+ if (!qemu_write_pidfile(pid_file, &err)) {
+ error_reportf_err(err, "cannot create PID file: ");
+ exit(EXIT_FAILURE);
+ }
+
+ atexit(pid_file_cleanup);
+}
+
int main(int argc, char *argv[])
{
#ifdef CONFIG_POSIX
@@ -312,6 +341,13 @@ int main(int argc, char *argv[])
qemu_init_main_loop(&error_fatal);
process_options(argc, argv);
+ /*
+ * Write the pid file after creating chardevs, exports, and NBD servers but
+ * before accepting connections. This ordering is documented. Do not change
+ * it.
+ */
+ pid_file_init();
+
while (!exit_requested) {
main_loop_wait(false);
}
--
2.29.2
- [PATCH v3] qemu-storage-daemon: add --pidfile option,
Stefan Hajnoczi <=