test: tests/bugs/rpc/bug-847624.t is crashed

Problem: glusterfs(GNFS) is crashing at the time of handling
         Pollerr event in rpcsvc_drc_client_unref.GNFS is crashed
         because ref was 0 at the time of unref and ref was taken
         while Pollin event successfully handled.

Solution: Convert drc_client ref to atomic ref to avoid the crash

Change-Id: Ia4c054f2f388032a5cd99597d0cfa18b003ca690
Fixes: #1038
Signed-off-by: Mohit Agrawal <moagrawal@redhat.com>

2 files changed, 8 insertions, 7 deletions

diff --git a/rpc/rpc-lib/src/rpc-drc.c b/rpc/rpc-lib/src/rpc-drc.c
index d083db24fc5..de8dc630626 100644
--- a/rpc/rpc-lib/src/rpc-drc.c
+++ b/rpc/rpc-lib/src/rpc-drc.c
@@ -190,7 +190,7 @@ rpcsvc_get_drc_client(rpcsvc_drc_globals_t *drc,
     if (!client)
         goto out;
 
-    client->ref = 0;
+    GF_ATOMIC_INIT(client->ref, 0);
     client->sock_union = (union gf_sock_union) * sockaddr;
     client->op_count = 0;
     INIT_LIST_HEAD(&client->client_list);
@@ -246,7 +246,7 @@ static drc_client_t *
 rpcsvc_drc_client_ref(drc_client_t *client)
 {
     GF_ASSERT(client);
-    client->ref++;
+    GF_ATOMIC_INC(client->ref);
     return client;
 }
 
@@ -261,11 +261,12 @@ rpcsvc_drc_client_ref(drc_client_t *client)
 static drc_client_t *
 rpcsvc_drc_client_unref(rpcsvc_drc_globals_t *drc, drc_client_t *client)
 {
+    uint32_t refcount;
+
     GF_ASSERT(drc);
-    GF_ASSERT(client->ref);
 
-    client->ref--;
-    if (!client->ref) {
+    refcount = GF_ATOMIC_DEC(client->ref);
+    if (!refcount) {
         drc->client_count--;
         rpcsvc_remove_drc_client(client);
         client = NULL;
@@ -589,7 +590,7 @@ rpcsvc_drc_priv(rpcsvc_drc_globals_t *drc)
         }
 
         gf_proc_dump_build_key(key, "client", "%d.ref_count", i);
-        gf_proc_dump_write(key, "%d", client->ref);
+        gf_proc_dump_write(key, "%" PRIu32, GF_ATOMIC_GET(client->ref));
         gf_proc_dump_build_key(key, "client", "%d.op_count", i);
         gf_proc_dump_write(key, "%d", client->op_count);
         i++;
diff --git a/rpc/rpc-lib/src/rpc-drc.h b/rpc/rpc-lib/src/rpc-drc.h
index 6aaede0828a..ce66430809b 100644
--- a/rpc/rpc-lib/src/rpc-drc.h
+++ b/rpc/rpc-lib/src/rpc-drc.h
@@ -24,7 +24,7 @@ struct drc_client {
     struct rb_table *rbtree;
     /* no. of ops currently cached */
     uint32_t op_count;
-    uint32_t ref;
+    gf_atomic_uint32_t ref;
     struct list_head client_list;
 };