From 3c6789fb8ba87810a2aa83eebf6eea10c969db6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sat, 26 Dec 2020 01:26:54 +0100
Subject: [PATCH] reaper: add optional callback
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When calling ‘reaper_add()’, the caller can provide a callback. If
non-NULL, the reaper will call the callback to handle the actual
reaping.

If the callback is NULL, or if it returns false, the reaper reaps the
child process.
---
 reaper.c | 54 +++++++++++++++++++++++++++++++++++-------------------
 reaper.h |  5 ++++-
 spawn.c  |  2 +-
 3 files changed, 40 insertions(+), 21 deletions(-)

diff --git a/reaper.c b/reaper.c
index 04a444f1..8ebd31a4 100644
--- a/reaper.c
+++ b/reaper.c
@@ -11,10 +11,16 @@
 #include "log.h"
 #include "tllist.h"
 
+struct child {
+    pid_t pid;
+    reaper_cb cb;
+    void *cb_data;
+};
+
 struct reaper {
     struct fdm *fdm;
     int fd;
-    tll(pid_t) children;
+    tll(struct child) children;
 };
 
 static bool fdm_reap(struct fdm *fdm, int fd, int events, void *data);
@@ -84,10 +90,12 @@ reaper_destroy(struct reaper *reaper)
 }
 
 void
-reaper_add(struct reaper *reaper, pid_t pid)
+reaper_add(struct reaper *reaper, pid_t pid, reaper_cb cb, void *cb_data)
 {
     LOG_DBG("adding pid=%d", pid);
-    tll_push_back(reaper->children, pid);
+    tll_push_back(
+        reaper->children,
+        ((struct child){.pid = pid, .cb = cb, .cb_data = cb_data}));
 }
 
 static bool
@@ -119,26 +127,34 @@ fdm_reap(struct fdm *fdm, int fd, int events, void *data)
     }
 
     tll_foreach(reaper->children, it) {
-        /* Don't use wait() since we don't want to accidentally reap
-         * the PTS slave */
+        struct child *child = &it->item;
+        pid_t pid = child->pid;
 
-        pid_t pid = it->item;
-
-        int result;
-        int res = waitpid(pid, &result, WNOHANG);
-
-        if (res <= 0) {
-            if (res < 0)
-                LOG_ERRNO("waitpid failed for pid=%d", pid);
+        if (pid != (pid_t)info.ssi_pid)
             continue;
+
+        bool reap_ourselves = true;
+        if (child->cb != NULL)
+            reap_ourselves = !child->cb(reaper, pid, child->cb_data);
+
+        if (reap_ourselves) {
+            int result;
+            int res = waitpid(pid, &result, WNOHANG);
+
+            if (res <= 0) {
+                if (res < 0)
+                    LOG_ERRNO("waitpid failed for pid=%d", pid);
+                continue;
+            }
+
+            else if (WIFEXITED(result))
+                LOG_DBG("pid=%d: exited with status=%d", pid, WEXITSTATUS(result));
+            else if (WIFSIGNALED(result))
+                LOG_DBG("pid=%d: killed by signal=%d", pid, WTERMSIG(result));
+            else
+                LOG_DBG("pid=%d: died of unknown resason", pid);
         }
 
-        else if (WIFEXITED(result))
-            LOG_DBG("pid=%d: exited with status=%d", pid, WEXITSTATUS(result));
-        else if (WIFSIGNALED(result))
-            LOG_DBG("pid=%d: killed by signal=%d", pid, WTERMSIG(result));
-        else
-            LOG_DBG("pid=%d: died of unknown resason", pid);
         tll_remove(reaper->children, it);
     }
 
diff --git a/reaper.h b/reaper.h
index 2daa9a8b..f955aa44 100644
--- a/reaper.h
+++ b/reaper.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <stdbool.h>
 #include <sys/wait.h>
 
 #include "fdm.h"
@@ -9,4 +10,6 @@ struct reaper;
 struct reaper *reaper_init(struct fdm *fdm);
 void reaper_destroy(struct reaper *reaper);
 
-void reaper_add(struct reaper *reaper, pid_t pid);
+typedef bool (*reaper_cb)(struct reaper *reaper, pid_t pid, void *data);
+
+void reaper_add(struct reaper *reaper, pid_t pid, reaper_cb cb, void *cb_data);
diff --git a/spawn.c b/spawn.c
index cc4755f4..6d96cf54 100644
--- a/spawn.c
+++ b/spawn.c
@@ -55,7 +55,7 @@ spawn(struct reaper *reaper, const char *cwd, char *const argv[],
     close(pipe_fds[0]);
 
     if (ret == 0) {
-        reaper_add(reaper, pid);
+        reaper_add(reaper, pid, NULL, NULL);
         return true;
     } else if (ret < 0) {
         LOG_ERRNO("failed to read from pipe");