rpc: Do not reset @ping_started to 0 in ping callback

This is to avoid indefinite recursion of the following kind, that could
lead to a stack overflow:

rpc_clnt_start_ping() -> rpc_clnt_ping() -> rpc_clnt_submit() ->
rpc_clnt_start_ping() -> rpc_clnt_ping() -> rpc_clnt_submit() ...
and so on,

since it is possible that before rpc_clnt_start_ping() is called a
second time by the thread executing this codepath, the response to
previous ping request could ALWAYS come by and cause epoll thread to
reset conn->ping_started to 0.

This patch also fixes the issue of excessive ping traffic, which was
due to the client sending one ping rpc for every fop in the worst case.

Also removed dead code in glusterd.

Change-Id: I7c5e6ae3b1c9d23407c0a12a319bdcb43ba7a359
BUG: 1116243
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/8257
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

3 files changed, 27 insertions, 12 deletions

diff --git a/rpc/rpc-lib/src/rpc-clnt-ping.c b/rpc/rpc-lib/src/rpc-clnt-ping.c
index 0ef54f8c6f8..948a244838e 100644
--- a/rpc/rpc-lib/src/rpc-clnt-ping.c
+++ b/rpc/rpc-lib/src/rpc-clnt-ping.c
@@ -35,6 +35,9 @@ struct rpc_clnt_program clnt_ping_prog = {
         .procnames = clnt_ping_procs,
 };
 
+static void
+rpc_clnt_start_ping (void *rpc_ptr);
+
 void
 rpc_clnt_ping_timer_expired (void *rpc_ptr)
 {
@@ -88,6 +91,7 @@ rpc_clnt_ping_timer_expired (void *rpc_ptr)
                         if (conn->ping_timer == NULL) {
                                 gf_log (trans->name, GF_LOG_WARNING,
                                         "unable to setup ping timer");
+                                conn->ping_started = 0;
                                 rpc_clnt_unref (rpc);
                         }
                 } else {
@@ -154,10 +158,6 @@ rpc_clnt_ping_cbk (struct rpc_req *req, struct iovec *iov, int count,
                         goto unlock;
                 }
 
-                /*This allows other RPCs to be able to start the ping timer
-                 * if they come by before the following start ping routine
-                 * is executed by the timer thread.*/
-                conn->ping_started = 0;
                 gf_timer_call_cancel (this->ctx,
                                       conn->ping_timer);
 
@@ -171,6 +171,7 @@ rpc_clnt_ping_cbk (struct rpc_req *req, struct iovec *iov, int count,
                 if (conn->ping_timer == NULL) {
                         gf_log (this->name, GF_LOG_WARNING,
                                 "failed to set the ping timer");
+                        conn->ping_started = 0;
                         rpc_clnt_unref (rpc);
                 }
 
@@ -214,7 +215,7 @@ fail:
 
 }
 
-void
+static void
 rpc_clnt_start_ping (void *rpc_ptr)
 {
         struct rpc_clnt         *rpc         = NULL;
@@ -233,14 +234,10 @@ rpc_clnt_start_ping (void *rpc_ptr)
 
         pthread_mutex_lock (&conn->lock);
         {
-                if (conn->ping_started) {
-                        pthread_mutex_unlock (&conn->lock);
-                        return;
-                }
-
                 if (conn->ping_timer) {
                         gf_timer_call_cancel (rpc->ctx, conn->ping_timer);
                         conn->ping_timer = NULL;
+                        conn->ping_started = 0;
                         rpc_clnt_unref (rpc);
                 }
 
@@ -284,3 +281,21 @@ rpc_clnt_start_ping (void *rpc_ptr)
 
         rpc_clnt_ping(rpc);
 }
+
+void
+rpc_clnt_check_and_start_ping (struct rpc_clnt *rpc)
+{
+        char start_ping = 0;
+
+        pthread_mutex_lock (&rpc->conn.lock);
+        {
+                if (!rpc->conn.ping_started)
+                        start_ping = 1;
+        }
+        pthread_mutex_unlock (&rpc->conn.lock);
+
+        if (start_ping)
+                rpc_clnt_start_ping ((void *)rpc);
+
+        return;
+}
diff --git a/rpc/rpc-lib/src/rpc-clnt-ping.h b/rpc/rpc-lib/src/rpc-clnt-ping.h
index 4edc416cee9..d7cd1d965e5 100644
--- a/rpc/rpc-lib/src/rpc-clnt-ping.h
+++ b/rpc/rpc-lib/src/rpc-clnt-ping.h
@@ -16,4 +16,4 @@
 
 #define RPC_DEFAULT_PING_TIMEOUT 30
 void
-rpc_clnt_start_ping (void *rpc_ptr);
+rpc_clnt_check_and_start_ping (struct rpc_clnt *rpc_ptr);
diff --git a/rpc/rpc-lib/src/rpc-clnt.c b/rpc/rpc-lib/src/rpc-clnt.c
index 8a460cfa617..b831c537723 100644
--- a/rpc/rpc-lib/src/rpc-clnt.c
+++ b/rpc/rpc-lib/src/rpc-clnt.c
@@ -1579,7 +1579,7 @@ rpc_clnt_submit (struct rpc_clnt *rpc, rpc_clnt_prog_t *prog,
                 goto out;
         }
 
-        rpc_clnt_start_ping (rpc);
+        rpc_clnt_check_and_start_ping (rpc);
         ret = 0;
 
 out: