changelog/rpc: Fix rpc_clnt_t mem leaks

PROBLEM:
   1. Freeing up rpc_clnt object might lead to crashes. Well,
      it was not a necessity to free rpc-clnt object till now
      because all the existing use cases needs to reconnect
      back on disconnects. Hence timer code was not taking
      ref on rpc-clnt object.

      Glusterd had some use-cases that led to crash due to
      ping-timer and they fixed only those code paths that
      involve ping-timer.

      Now, since changelog has an use-case where rpc-clnt
      need to be freed up, we need to fix timer code to take
      refs

   2. In changelog, because of issue 1, only mydata was being
      freed which is incorrect. And there are races where
      rpc-clnt object would access the freed mydata which
      would lead to crashes.

      Since changelog xlator resides on brick side and is long
      living process, if multiple libgfchangelog consumers
      register to changelog and disconnect/reconnect mulitple
      times, it would result in leak of 'rpc-clnt' object
      for every connect/disconnect.

SOLUTION:
   1. Handle ref/unref of 'rpc_clnt' structure in timer
      functions properly.
   2. In changelog, unref 'rpc_clnt' in RPC_CLNT_DISCONNECT
      after disabling timers and free mydata on RPC_CLNT_DESTROY.

RPC SETUP IN CHANGELOG:
   1. changelog xlator initiates rpc server say 'changelog_rpc_server'
   2. libgfchangelog initiates one rpc server say 'libgfchangelog_rpc_server'
   3. libgfchangelog initiates rpc client and connects to 'changelog_rpc_server'
   4. In return changelog_rpc_server initiates a rpc client and connects back
      to 'libgfchangelog_rpc_server'

REF/UNREF HANDLING IN TIMER FUNCTIONS:
Let's say rpc clnt refcount = 1
   1. Take the ref before reigstering callback to timer queue
           >>>>  rpc_clnt_ref (say ref count becomes = 2)
   2. Register a callback to timer say 'callback1'
   3. If register fails:
           >>>> rpc_clnt_unref (ref count = 1)
   4. On timer expiration, 'callback1' gets called. So unref rpc clnt at the end
      in 'callback1'. This is corresponding to ref taken in step 1
           >>>> rpc_clnt_unref (ref count = 1)
   5. The cycle from step-1 to step-4 continues....until timer cancel event happens
   6. timer cancel of say 'callback1'
           If timer cancel fails:
                 Do nothing, Step-4 would have unrefd
           If timer cancel succeeds:
                 >>>> rpc_clnt_unref (ref count = 1)

Change-Id: I91389bc511b8b1a17824941970ee8d2c29a74a09
BUG: 1316178
Signed-off-by: Kotresh HR <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/13658
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>

2 files changed, 99 insertions, 6 deletions

diff --git a/rpc/rpc-lib/src/rpc-clnt.c b/rpc/rpc-lib/src/rpc-clnt.c
index 27e394093cf..a9e43eb42f1 100644
--- a/rpc/rpc-lib/src/rpc-clnt.c
+++ b/rpc/rpc-lib/src/rpc-clnt.c
@@ -121,6 +121,7 @@ call_bail (void *data)
         struct timespec        timeout = {0,};
         struct iovec           iov = {0,};
         char                   peerid[UNIX_PATH_MAX] = {0};
+        gf_boolean_t           need_unref = _gf_false;
 
         GF_VALIDATE_OR_GOTO ("client", data, out);
 
@@ -153,6 +154,8 @@ call_bail (void *data)
                         timeout.tv_sec = 10;
                         timeout.tv_nsec = 0;
 
+                        /* Ref rpc as it's added to timer event queue */
+                        rpc_clnt_ref (clnt);
                         gf_timer_call_cancel (clnt->ctx, conn->timer);
                         conn->timer = gf_timer_call_after (clnt->ctx,
                                                            timeout,
@@ -163,6 +166,7 @@ call_bail (void *data)
                                 gf_log (conn->name, GF_LOG_WARNING,
                                         "Cannot create bailout timer for %s",
                                         peerid);
+                                need_unref = _gf_true;
                         }
                 }
 
@@ -205,6 +209,9 @@ call_bail (void *data)
                 mem_put (trav);
         }
 out:
+        rpc_clnt_unref (clnt);
+        if (need_unref)
+                rpc_clnt_unref (clnt);
         return;
 }
 
@@ -230,6 +237,7 @@ __save_frame (struct rpc_clnt *rpc_clnt, call_frame_t *frame,
         if (conn->timer == NULL) {
                 timeout.tv_sec  = 10;
                 timeout.tv_nsec = 0;
+                rpc_clnt_ref (rpc_clnt);
                 conn->timer = gf_timer_call_after (rpc_clnt->ctx,
                                                    timeout,
                                                    call_bail,
@@ -389,6 +397,7 @@ rpc_clnt_reconnect (void *conn_ptr)
         struct timespec          ts    = {0, 0};
         int32_t                  ret   = 0;
         struct rpc_clnt         *clnt  = NULL;
+        gf_boolean_t             need_unref = _gf_false;
 
         conn  = conn_ptr;
         clnt = conn->rpc_clnt;
@@ -413,10 +422,16 @@ rpc_clnt_reconnect (void *conn_ptr)
                                 "attempting reconnect");
                         ret = rpc_transport_connect (trans,
                                                      conn->config.remote_port);
+                        rpc_clnt_ref (clnt);
                         conn->reconnect =
                                 gf_timer_call_after (clnt->ctx, ts,
                                                      rpc_clnt_reconnect,
                                                      conn);
+                        if (!conn->reconnect) {
+                                need_unref = _gf_true;
+                                gf_log (conn->name, GF_LOG_ERROR,
+                                        "Error adding to timer event queue");
+                        }
                 } else {
                         gf_log (conn->name, GF_LOG_TRACE,
                                 "breaking reconnect chain");
@@ -424,6 +439,9 @@ rpc_clnt_reconnect (void *conn_ptr)
         }
         pthread_mutex_unlock (&conn->lock);
 
+        rpc_clnt_unref (clnt);
+        if (need_unref)
+                rpc_clnt_unref (clnt);
         return;
 }
 
@@ -463,6 +481,8 @@ int
 rpc_clnt_reconnect_cleanup (rpc_clnt_connection_t *conn)
 {
         struct rpc_clnt         *clnt  = NULL;
+        int                      ret   = 0;
+        gf_boolean_t             reconnect_unref = _gf_false;
 
         if (!conn) {
                 goto out;
@@ -474,13 +494,18 @@ rpc_clnt_reconnect_cleanup (rpc_clnt_connection_t *conn)
         {
 
                 if (conn->reconnect) {
-                        gf_timer_call_cancel (clnt->ctx, conn->reconnect);
+                        ret = gf_timer_call_cancel (clnt->ctx, conn->reconnect);
+                        if (!ret)
+                                reconnect_unref = _gf_true;
                         conn->reconnect = NULL;
                 }
 
         }
         pthread_mutex_unlock (&conn->lock);
 
+        if (reconnect_unref)
+                rpc_clnt_unref (clnt);
+
 out:
         return 0;
 }
@@ -496,6 +521,8 @@ rpc_clnt_connection_cleanup (rpc_clnt_connection_t *conn)
         struct saved_frames    *saved_frames = NULL;
         struct rpc_clnt         *clnt  = NULL;
         int                     unref = 0;
+        int                     ret   = 0;
+        gf_boolean_t            timer_unref = _gf_false;
 
         if (!conn) {
                 goto out;
@@ -511,7 +538,9 @@ rpc_clnt_connection_cleanup (rpc_clnt_connection_t *conn)
 
                 /* bailout logic cleanup */
                 if (conn->timer) {
-                        gf_timer_call_cancel (clnt->ctx, conn->timer);
+                        ret = gf_timer_call_cancel (clnt->ctx, conn->timer);
+                        if (!ret)
+                                timer_unref = _gf_true;
                         conn->timer = NULL;
                 }
 
@@ -528,6 +557,9 @@ rpc_clnt_connection_cleanup (rpc_clnt_connection_t *conn)
         if (unref)
                 rpc_clnt_unref (clnt);
 
+        if (timer_unref)
+                rpc_clnt_unref (clnt);
+
 out:
         return 0;
 }
@@ -851,6 +883,7 @@ rpc_clnt_notify (rpc_transport_t *trans, void *mydata,
         rpc_transport_pollin_t *pollin      = NULL;
         struct timespec         ts          = {0, };
         void                   *clnt_mydata = NULL;
+        gf_boolean_t            unref_clnt  = _gf_false;
         DECLARE_OLD_THIS;
 
         conn = mydata;
@@ -875,10 +908,16 @@ rpc_clnt_notify (rpc_transport_t *trans, void *mydata,
                                 ts.tv_sec = 10;
                                 ts.tv_nsec = 0;
 
+                                rpc_clnt_ref (clnt);
                                 conn->reconnect =
                                         gf_timer_call_after (clnt->ctx, ts,
                                                              rpc_clnt_reconnect,
                                                              conn);
+                                if (conn->reconnect == NULL) {
+                                        gf_log (conn->name, GF_LOG_WARNING,
+                                                "Cannot create rpc_clnt_reconnect timer");
+                                        unref_clnt = _gf_true;
+                                }
                         }
                 }
                 pthread_mutex_unlock (&conn->lock);
@@ -886,6 +925,9 @@ rpc_clnt_notify (rpc_transport_t *trans, void *mydata,
                 if (clnt->notifyfn)
                         ret = clnt->notifyfn (clnt, clnt->mydata,
                                               RPC_CLNT_DISCONNECT, NULL);
+                if (unref_clnt)
+                        rpc_clnt_ref (clnt);
+
                 break;
         }
 
@@ -1135,6 +1177,10 @@ rpc_clnt_start (struct rpc_clnt *rpc)
                 rpc->disabled = 0;
         }
         pthread_mutex_unlock (&conn->lock);
+        /* Corresponding unref will be either on successful timer cancel or last
+         * rpc_clnt_reconnect fire event.
+         */
+        rpc_clnt_ref (rpc);
         rpc_clnt_reconnect (conn);
 
         return 0;
@@ -1512,6 +1558,7 @@ rpc_clnt_submit (struct rpc_clnt *rpc, rpc_clnt_prog_t *prog,
         int                    proglen     = 0;
         char                   new_iobref  = 0;
         uint64_t               callid      = 0;
+        gf_boolean_t           need_unref  = _gf_false;
 
         if (!rpc || !prog || !frame) {
                 goto out;
@@ -1596,6 +1643,14 @@ rpc_clnt_submit (struct rpc_clnt *rpc, rpc_clnt_prog_t *prog,
                 if ((ret >= 0) && frame) {
                         /* Save the frame in queue */
                         __save_frame (rpc, frame, rpcreq);
+
+                        /* A ref on rpc-clnt object is taken while registering
+                         * call_bail to timer in __save_frame. If it fails to
+                         * register, it needs an unref and should happen outside
+                         * conn->lock which otherwise leads to deadlocks */
+                        if (conn->timer == NULL)
+                                need_unref = _gf_true;
+
                         conn->msgcnt++;
 
                         gf_log ("rpc-clnt", GF_LOG_TRACE, "submitted request "
@@ -1607,6 +1662,9 @@ rpc_clnt_submit (struct rpc_clnt *rpc, rpc_clnt_prog_t *prog,
         }
         pthread_mutex_unlock (&conn->lock);
 
+        if (need_unref)
+                rpc_clnt_unref (rpc);
+
         if (ret == -1) {
                 goto out;
         }
@@ -1739,6 +1797,9 @@ rpc_clnt_disable (struct rpc_clnt *rpc)
         rpc_clnt_connection_t *conn = NULL;
         rpc_transport_t       *trans = NULL;
         int                    unref = 0;
+        int                    ret   = 0;
+        gf_boolean_t           timer_unref = _gf_false;
+        gf_boolean_t           reconnect_unref = _gf_false;
 
         if (!rpc) {
                 goto out;
@@ -1751,12 +1812,20 @@ rpc_clnt_disable (struct rpc_clnt *rpc)
                 rpc->disabled = 1;
 
                 if (conn->timer) {
-                        gf_timer_call_cancel (rpc->ctx, conn->timer);
+                        ret = gf_timer_call_cancel (rpc->ctx, conn->timer);
+                        /* If the event is not fired and it actually cancelled
+                         * the timer, do the unref else registered call back
+                         * function will take care of it.
+                         */
+                        if (!ret)
+                                timer_unref = _gf_true;
                         conn->timer = NULL;
                 }
 
                 if (conn->reconnect) {
-                        gf_timer_call_cancel (rpc->ctx, conn->reconnect);
+                        ret = gf_timer_call_cancel (rpc->ctx, conn->reconnect);
+                        if (!ret)
+                                reconnect_unref = _gf_true;
                         conn->reconnect = NULL;
                 }
                 conn->connected = 0;
@@ -1774,6 +1843,12 @@ rpc_clnt_disable (struct rpc_clnt *rpc)
         if (unref)
                 rpc_clnt_unref (rpc);
 
+        if (timer_unref)
+                rpc_clnt_unref (rpc);
+
+        if (reconnect_unref)
+                rpc_clnt_unref (rpc);
+
 out:
         return;
 }
@@ -1784,6 +1859,9 @@ rpc_clnt_disconnect (struct rpc_clnt *rpc)
         rpc_clnt_connection_t *conn  = NULL;
         rpc_transport_t       *trans = NULL;
         int                    unref = 0;
+        int                    ret   = 0;
+        gf_boolean_t           timer_unref = _gf_false;
+        gf_boolean_t           reconnect_unref = _gf_false;
 
         if (!rpc)
                 goto out;
@@ -1794,12 +1872,20 @@ rpc_clnt_disconnect (struct rpc_clnt *rpc)
         {
                 rpc->disabled = 1;
                 if (conn->timer) {
-                        gf_timer_call_cancel (rpc->ctx, conn->timer);
+                        ret = gf_timer_call_cancel (rpc->ctx, conn->timer);
+                        /* If the event is not fired and it actually cancelled
+                         * the timer, do the unref else registered call back
+                         * function will take care of unref.
+                         */
+                        if (!ret)
+                                timer_unref = _gf_true;
                         conn->timer = NULL;
                 }
 
                 if (conn->reconnect) {
-                        gf_timer_call_cancel (rpc->ctx, conn->reconnect);
+                        ret = gf_timer_call_cancel (rpc->ctx, conn->reconnect);
+                        if (!ret)
+                                reconnect_unref = _gf_true;
                         conn->reconnect = NULL;
                 }
                 conn->connected = 0;
@@ -1815,6 +1901,12 @@ rpc_clnt_disconnect (struct rpc_clnt *rpc)
         if (unref)
                 rpc_clnt_unref (rpc);
 
+        if (timer_unref)
+                rpc_clnt_unref (rpc);
+
+        if (reconnect_unref)
+                rpc_clnt_unref (rpc);
+
 out:
         return;
 }
diff --git a/rpc/rpc-lib/src/rpc-clnt.h b/rpc/rpc-lib/src/rpc-clnt.h
index 01caeb814c0..f84b4cbf806 100644
--- a/rpc/rpc-lib/src/rpc-clnt.h
+++ b/rpc/rpc-lib/src/rpc-clnt.h
@@ -231,6 +231,7 @@ struct rpc_clnt *
 rpc_clnt_unref (struct rpc_clnt *rpc);
 
 int rpc_clnt_connection_cleanup (rpc_clnt_connection_t *conn);
+int rpc_clnt_reconnect_cleanup (rpc_clnt_connection_t *conn);
 
 void rpc_clnt_set_connected (rpc_clnt_connection_t *conn);