From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
Date: Mon, 30 Oct 2017 16:10:37 +0000 (+0000)
Subject: core: remove "misuse" of getpgid() in systemd-shutdown
X-Git-Tag: v236~277^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fpull%2F7226%2Fhead;p=thirdparty%2Fsystemd.git

core: remove "misuse" of getpgid() in systemd-shutdown

Using `kill()`  with a signal of 0 is a slightly more documented idiom for
checking whether a process still exists.  It is mentioned explicitly in
man pages.  This avoids the need to comment the call as "misuse".
A comment is still necessary - in fact this idiom is even more confusing if
you don't know how it works.  But it's easy enough to explain.
---

diff --git a/src/core/killall.c b/src/core/killall.c
index 5e914e478d3..fe5320e8136 100644
--- a/src/core/killall.c
+++ b/src/core/killall.c
@@ -129,9 +129,9 @@ static void wait_for_children(Set *pids, sigset_t *mask) {
                  * might not be our child. */
                 SET_FOREACH(p, pids, i) {
 
-                        /* We misuse getpgid as a check whether a
-                         * process still exists. */
-                        if (getpgid(PTR_TO_PID(p)) >= 0)
+                        /* kill(pid, 0) sends no signal, but it tells
+                         * us whether the process still exists. */
+                        if (kill(PTR_TO_PID(p), 0) == 0)
                                 continue;
 
                         if (errno != ESRCH)