From 7be917058560c2281a1ee891cb6ff6a7b8de345b Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 13 Nov 2015 09:31:01 +0100
Subject: [PATCH] Lua debugger: handle forked sessions children during
 shutdown.

---
 src/scripting.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 src/server.c    | 12 ++++++++----
 src/server.h    |  2 ++
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/src/scripting.c b/src/scripting.c
index 8fcf40dc..d071e59a 100644
--- a/src/scripting.c
+++ b/src/scripting.c
@@ -63,6 +63,7 @@ struct ldbState {
     int forked; /* Is this a fork()ed debugging session? */
     list *logs; /* List of messages to send to the client. */
     list *traces; /* Messages about Redis commands executed since last stop.*/
+    list *children; /* All forked debugging sessions pids. */
     int bp[LDB_BREAKPOINTS_MAX]; /* An array of breakpoints line numbers. */
     int bpcount; /* Number of valid entries inside bp. */
     int step;   /* Stop at next line ragardless of breakpoints. */
@@ -1489,6 +1490,7 @@ void ldbInit(void) {
     ldb.active = 0;
     ldb.logs = listCreate();
     listSetFreeMethod(ldb.logs,(void (*)(void*))sdsfree);
+    ldb.children = listCreate();
     ldb.src = NULL;
     ldb.lines = 0;
     ldb.cbuf = sdsempty();
@@ -1560,11 +1562,22 @@ int ldbStartSession(client *c) {
             addReplyError(c,"Fork() failed: can't run EVAL in debugging mode.");
             return 0;
         } else if (cp == 0) {
-            /* Child */
+            /* Child. Let's ignore important signals handled by the parent. */
+            struct sigaction act;
+            sigemptyset(&act.sa_mask);
+            act.sa_flags = 0;
+            act.sa_handler = SIG_IGN;
+            sigaction(SIGTERM, &act, NULL);
+            sigaction(SIGINT, &act, NULL);
+
+            /* Log the creation of the child and close the listening
+             * socket to make sure if the parent crashes a reset is sent
+             * to the clients. */
             serverLog(LL_WARNING,"Redis forked for debugging eval");
             closeListeningSockets(0);
         } else {
             /* Parent */
+            listAddNodeTail(ldb.children,(void*)(unsigned long)cp);
             freeClientAsync(c); /* Close the client in the parent side. */
             return 0;
         }
@@ -1618,6 +1631,33 @@ void ldbEndSession(client *c) {
     ldb.active = 0;
 }
 
+/* If the specified pid is among the list of children spawned for
+ * forked debugging sessions, it is removed from the children list.
+ * If the pid was found non-zero is returned. */
+int ldbRemoveChild(pid_t pid) {
+    listNode *ln = listSearchKey(ldb.children,(void*)(unsigned long)pid);
+    if (ln) {
+        listDelNode(ldb.children,ln);
+        return 1;
+    }
+    return 0;
+}
+
+/* Kill all the forked sessions. */
+void ldbKillForkedSessions(void) {
+    listIter li;
+    listNode *ln;
+
+    listRewind(ldb.children,&li);
+    while((ln = listNext(&li))) {
+        pid_t pid = (unsigned long) ln->value;
+        serverLog(LL_WARNING,"Killing debugging session %ld",(long)pid);
+        kill(pid,SIGKILL);
+    }
+    listRelease(ldb.children);
+    ldb.children = listCreate();
+}
+
 /* Wrapper for EVAL / EVALSHA that enables debugging, and makes sure
  * that when EVAL returns, whatever happened, the session is ended. */
 void evalGenericCommandWithDebugging(client *c, int evalsha) {
diff --git a/src/server.c b/src/server.c
index b74726df..e6844c78 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1201,10 +1201,11 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
             } else if (pid == server.aof_child_pid) {
                 backgroundRewriteDoneHandler(exitcode,bysignal);
             } else {
-                serverLog(LL_WARNING,
-                    "Warning, detected child with unmatched pid: %ld"
-                    " (EVAL forked debugging session?)",
-                    (long)pid);
+                if (!ldbRemoveChild(pid)) {
+                    serverLog(LL_WARNING,
+                        "Warning, detected child with unmatched pid: %ld",
+                        (long)pid);
+                }
             }
             updateDictResizePolicy();
         }
@@ -2528,6 +2529,9 @@ int prepareForShutdown(int flags) {
 
     serverLog(LL_WARNING,"User requested shutdown...");
 
+    /* Kill all the Lua debugger forked sessions. */
+    ldbKillForkedSessions();
+
     /* Kill the saving child if there is a background saving in progress.
        We want to avoid race conditions, for instance our saving child may
        overwrite the synchronous saving did by SHUTDOWN. */
diff --git a/src/server.h b/src/server.h
index cb252dda..96004fa1 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1471,6 +1471,8 @@ int redis_check_rdb_main(char **argv, int argc);
 
 /* Scripting */
 void scriptingInit(int setup);
+int ldbRemoveChild(pid_t pid);
+void ldbKillForkedSessions(void);
 
 /* Blocked clients */
 void processUnblockedClients(void);