[systemd-devel] [PATCH] core: fix detection of dead process.

[Yuxuan Shui]

Commit 5ba6985b moves the UNIT_VTABLE(u)->sigchld_event before systemd
actually reap the zombie. Which leads to service_load_pid_file accept
zombie as a valid pid.
---
 src/core/service.c |  3 +++
 src/shared/util.c  | 24 ++++++++++++++++++++++++
 src/shared/util.h  |  1 +
 3 files changed, 28 insertions(+)

diff --git a/src/core/service.c b/src/core/service.c
index 5129784..64a0670 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -1376,6 +1376,9 @@ static int service_load_pid_file(Service *s, bool may_warn) {
                 return -ESRCH;
         }
 
+        if ('Z' == get_process_state(pid))
+                return -ESRCH;
+
         if (s->main_pid_known) {
                 if (pid == s->main_pid)
                         return 0;
diff --git a/src/shared/util.c b/src/shared/util.c
index 3482b9b..6c3cf6c 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -513,6 +513,30 @@ char *truncate_nl(char *s) {
         return s;
 }
 
+char get_process_state(pid_t pid) {
+        const char *p;
+        int r;
+
+        assert(name);
+        assert(pid >= 0);
+
+        p = procfs_file_alloca(pid, "stat");
+        r = read_one_line_file(p, &line);
+        if (r < 0)
+                return r;
+
+        p = strrchr(line, ')');
+        if (!p)
+                return -EIO;
+
+        p++;
+
+        if (sscanf(p, " %c", &state) != 1)
+                return -EIO;
+
+        return state;
+}
+
 int get_process_comm(pid_t pid, char **name) {
         const char *p;
         int r;
diff --git a/src/shared/util.h b/src/shared/util.h
index 9aea3a4..8dede1f 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -238,6 +238,7 @@ char *file_in_same_dir(const char *path, const char *filename);
 
 int rmdir_parents(const char *path, const char *stop);
 
+char get_process_state(pid_t pid);
 int get_process_comm(pid_t pid, char **name);
 int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char **line);
 int get_process_exe(pid_t pid, char **name);
-- 
1.8.5.4