From 6fb97a85c79addac8f25d90e04296cb658f8ed27 Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Wed, 22 May 2024 00:23:50 +0800
Subject: [PATCH 1/2] process-util: make pid*_get_start_time return usec_t

---
 src/basic/process-util.c     | 12 ++++++------
 src/basic/process-util.h     |  4 ++--
 src/test/test-process-util.c |  8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index c9d968dee0a..15839cb4473 100644
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -56,6 +56,7 @@
 #include "string-table.h"
 #include "string-util.h"
 #include "terminal-util.h"
+#include "time-util.h"
 #include "user-util.h"
 #include "utf8.h"
 
@@ -731,7 +732,7 @@ int get_process_ppid(pid_t pid, pid_t *ret) {
         return 0;
 }
 
-int pid_get_start_time(pid_t pid, uint64_t *ret) {
+int pid_get_start_time(pid_t pid, usec_t *ret) {
         _cleanup_free_ char *line = NULL;
         const char *p;
         int r;
@@ -751,13 +752,12 @@ int pid_get_start_time(pid_t pid, uint64_t *ret) {
         p = strrchr(line, ')');
         if (!p)
                 return -EIO;
-
         p++;
 
         unsigned long llu;
 
         if (sscanf(p, " "
-                   "%*c "  /* state */
+                   "%*c " /* state */
                    "%*u " /* ppid */
                    "%*u " /* pgrp */
                    "%*u " /* session */
@@ -781,13 +781,13 @@ int pid_get_start_time(pid_t pid, uint64_t *ret) {
                 return -EIO;
 
         if (ret)
-                *ret = llu;
+                *ret = jiffies_to_usec(llu); /* CLOCK_BOOTTIME */
 
         return 0;
 }
 
-int pidref_get_start_time(const PidRef *pid, uint64_t *ret) {
-        uint64_t t;
+int pidref_get_start_time(const PidRef *pid, usec_t *ret) {
+        usec_t t;
         int r;
 
         if (!pidref_is_set(pid))
diff --git a/src/basic/process-util.h b/src/basic/process-util.h
index 83084028478..cbcb91b6eb0 100644
--- a/src/basic/process-util.h
+++ b/src/basic/process-util.h
@@ -54,8 +54,8 @@ int get_process_cwd(pid_t pid, char **ret);
 int get_process_root(pid_t pid, char **ret);
 int get_process_environ(pid_t pid, char **ret);
 int get_process_ppid(pid_t pid, pid_t *ret);
-int pid_get_start_time(pid_t pid, uint64_t *ret);
-int pidref_get_start_time(const PidRef* pid, uint64_t *ret);
+int pid_get_start_time(pid_t pid, usec_t *ret);
+int pidref_get_start_time(const PidRef* pid, usec_t *ret);
 int get_process_umask(pid_t pid, mode_t *ret);
 
 int container_get_leader(const char *machine, pid_t *pid);
diff --git a/src/test/test-process-util.c b/src/test/test-process-util.c
index c96bd4341bc..563d5a0fe76 100644
--- a/src/test/test-process-util.c
+++ b/src/test/test-process-util.c
@@ -951,18 +951,18 @@ TEST(pid_get_start_time) {
 
         assert_se(pidref_set_self(&pidref) >= 0);
 
-        uint64_t start_time;
+        usec_t start_time;
         assert_se(pidref_get_start_time(&pidref, &start_time) >= 0);
-        log_info("our starttime: %" PRIu64, start_time);
+        log_info("our starttime: " USEC_FMT, start_time);
 
         _cleanup_(pidref_done_sigkill_wait) PidRef child = PIDREF_NULL;
 
         assert_se(pidref_safe_fork("(stub)", FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS, &child) >= 0);
 
-        uint64_t start_time2;
+        usec_t start_time2;
         assert_se(pidref_get_start_time(&child, &start_time2) >= 0);
 
-        log_info("child starttime: %" PRIu64, start_time2);
+        log_info("child starttime: " USEC_FMT, start_time2);
 
         assert_se(start_time2 >= start_time);
 }

From f781292d6cfd1319a2be0194d5dca4703ea025a3 Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Tue, 21 May 2024 23:43:06 +0800
Subject: [PATCH 2/2] core/service: try to query for new main process's
 starttime

Currently, when service_set_main_pidref() is called
without specifying start_timestamp, exec_status_start()
always uses dual_timestamp_now(). This is not ideal,
though, as when the main pid changes halfway due to
e.g. sd_notify + MAINPID=, it's definitely spurious.
---
 src/core/service.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/core/service.c b/src/core/service.c
index 8ec27c463a4..3ccb05bff46 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -214,6 +214,16 @@ static int service_set_main_pidref(Service *s, PidRef pidref_consume, const dual
 
         if (!pidref_equal(&s->main_pid, &pidref)) {
                 service_unwatch_main_pid(s);
+
+                dual_timestamp pid_start_time;
+
+                if (!start_timestamp) {
+                        usec_t t;
+
+                        if (pidref_get_start_time(&pidref, &t) >= 0)
+                                start_timestamp = dual_timestamp_from_boottime(&pid_start_time, t);
+                }
+
                 exec_status_start(&s->main_exec_status, pidref.pid, start_timestamp);
         }