From 940d9b963644b835ec5d4f2b9cf627c2e3a6d915 Mon Sep 17 00:00:00 2001
From: Wilfried Goesgens <dothebart@citadel.org>
Date: Fri, 7 Nov 2014 00:38:18 +0100
Subject: [PATCH] Instead of initiating the transition between DB & IO-Queue
 from within the application logic, we now only prepare the swap and let the
 control-logic handle the transition. By this we avoid possible race
 conditions.

---
 citadel/event_client.c                        | 45 +++++++++++++------
 citadel/event_client.h                        |  4 +-
 .../modules/eventclient/serv_eventclient.c    |  7 +++
 3 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/citadel/event_client.c b/citadel/event_client.c
index c46429337..bdb33dd73 100644
--- a/citadel/event_client.c
+++ b/citadel/event_client.c
@@ -86,7 +86,7 @@ extern struct ev_loop *event_db;
 extern ev_async DBAddJob;
 extern ev_async DBExitEventLoop;
 
-eNextState QueueDBOperation(AsyncIO *IO, IO_CallBack CB)
+eNextState QueueAnDBOperation(AsyncIO *IO)
 {
 	IOAddHandler *h;
 	int i;
@@ -94,7 +94,10 @@ eNextState QueueDBOperation(AsyncIO *IO, IO_CallBack CB)
 	SetEVState(IO, eDBQ);
 	h = (IOAddHandler*)malloc(sizeof(IOAddHandler));
 	h->IO = IO;
-	h->EvAttch = CB;
+
+	assert(IO->ReAttachCB != NULL);
+
+	h->EvAttch = IO->ReAttachCB;
 	ev_cleanup_init(&IO->db_abort_by_shutdown,
 			IO_abort_shutdown_callback);
 	IO->db_abort_by_shutdown.data = IO;
@@ -219,7 +222,7 @@ static void IO_abort_shutdown_callback(struct ev_loop *loop,
 }
 
 
-eNextState QueueEventContext(AsyncIO *IO, IO_CallBack CB)
+eNextState QueueAnEventContext(AsyncIO *IO)
 {
 	IOAddHandler *h;
 	int i;
@@ -227,7 +230,11 @@ eNextState QueueEventContext(AsyncIO *IO, IO_CallBack CB)
 	SetEVState(IO, eIOQ);
 	h = (IOAddHandler*)malloc(sizeof(IOAddHandler));
 	h->IO = IO;
-	h->EvAttch = CB;
+
+	assert(IO->ReAttachCB != NULL);
+
+	h->EvAttch = IO->ReAttachCB;
+
 	ev_cleanup_init(&IO->abort_by_shutdown,
 			IO_abort_shutdown_callback);
 	IO->abort_by_shutdown.data = IO;
@@ -260,12 +267,20 @@ eNextState QueueEventContext(AsyncIO *IO, IO_CallBack CB)
 eNextState EventQueueDBOperation(AsyncIO *IO, IO_CallBack CB, int CloseFDs)
 {
 	StopClientWatchers(IO, CloseFDs);
-	return QueueDBOperation(IO, CB);
+	IO->ReAttachCB = CB;
+	return eDBQuery;
 }
 eNextState DBQueueEventContext(AsyncIO *IO, IO_CallBack CB)
 {
 	StopDBWatchers(IO);
-	return QueueEventContext(IO, CB);
+	IO->ReAttachCB = CB;
+	return eSendReply;
+}
+
+eNextState QueueEventContext(AsyncIO *IO, IO_CallBack CB)
+{
+	IO->ReAttachCB = CB;
+	return QueueAnEventContext(IO);
 }
 
 extern eNextState evcurl_handle_start(AsyncIO *IO);
@@ -310,7 +325,8 @@ eNextState QueueCurlContext(AsyncIO *IO)
 eNextState CurlQueueDBOperation(AsyncIO *IO, IO_CallBack CB)
 {
 	StopCurlWatchers(IO);
-	return QueueDBOperation(IO, CB);
+	IO->ReAttachCB = CB;
+	return eDBQuery;
 }
 
 
@@ -497,13 +513,12 @@ eReadState HandleInbound(AsyncIO *IO)
 			assert(IO->ReadDone);
 			ev_io_stop(event_base, &IO->recv_event);
 			rc = IO->ReadDone(IO);
-			if  (rc != eDBQuery) {
-				IO->NextState = rc;
-				Finished = StrBufCheckBuffer(&IO->RecvBuf);
+			if  (rc == eDBQuery) {
+				return QueueAnDBOperation(IO);
 			}
 			else {
-				return rc;
-
+				IO->NextState = rc;
+				Finished = StrBufCheckBuffer(&IO->RecvBuf);
 			}
 		}
 	}
@@ -1239,10 +1254,12 @@ void KillAsyncIOContext(AsyncIO *IO)
 	case eReadMore:
 	case eReadPayload:
 	case eReadFile:
-		QueueEventContext(&Ctx->IO, KillOtherContextNow);
+		IO->ReAttachCB = KillOtherContextNow;
+		QueueAnEventContext(&Ctx->IO);
 		break;
 	case eDBQuery:
-		QueueDBOperation(&Ctx->IO, KillOtherContextNow);
+		IO->ReAttachCB = KillOtherContextNow;
+		QueueAnDBOperation(&Ctx->IO);
 		break;
 	case eTerminateConnection:
 	case eAbort:
diff --git a/citadel/event_client.h b/citadel/event_client.h
index 8777a3433..b21e2cc14 100644
--- a/citadel/event_client.h
+++ b/citadel/event_client.h
@@ -193,7 +193,8 @@ struct AsyncIO {
 		Timeout,      /* Timeout handler;may also be conn. timeout */
 		ConnFail,     /* What to do when one connection failed? */
 		ShutdownAbort,/* we're going down. make your piece. */
-		NextDBOperation; /* Perform Database IO */
+		NextDBOperation, /* Perform Database IO */
+		ReAttachCB;   /* on the hop from one Q to the other, this is the next CB */
 
 	/* if we have linereaders, maybe we want to read more lines before
 	 * the real application logic is called? */
@@ -282,7 +283,6 @@ extern int DebugCAres;
 void FreeAsyncIOContents(AsyncIO *IO);
 
 eNextState NextDBOperation(AsyncIO *IO, IO_CallBack CB);
-eNextState QueueDBOperation(AsyncIO *IO, IO_CallBack CB);
 eNextState EventQueueDBOperation(AsyncIO *IO, IO_CallBack CB, int CloseFDs);
 void StopDBWatchers(AsyncIO *IO);
 eNextState QueueEventContext(AsyncIO *IO, IO_CallBack CB);
diff --git a/citadel/modules/eventclient/serv_eventclient.c b/citadel/modules/eventclient/serv_eventclient.c
index 4a27c2482..942234afd 100644
--- a/citadel/modules/eventclient/serv_eventclient.c
+++ b/citadel/modules/eventclient/serv_eventclient.c
@@ -107,6 +107,8 @@ typedef struct _evcurl_global_data {
 ev_async WakeupCurl;
 evcurl_global_data global;
 
+eNextState QueueAnDBOperation(AsyncIO *IO);
+
 static void
 gotstatus(int nnrun)
 {
@@ -200,6 +202,11 @@ gotstatus(int nnrun)
 			switch(IO->SendDone(IO))
 			{
 			case eDBQuery:
+				curl_easy_cleanup(IO->HttpReq.chnd);
+				IO->HttpReq.chnd = NULL;
+				FreeURL(&IO->ConnectMe);
+				QueueAnDBOperation(IO);
+				break;
 			case eSendDNSQuery:
 			case eReadDNSReply:
 			case eConnect:
-- 
2.30.2