fdl: fix race during initialization

There was a race between fdl_worker starting to run and setting
this->private in fdl_init.  This should never happen on a
multiprocessor, since the new thread should start on a different core
and creating it there should take many times longer than getting from
pthread_create to the end of fdl_init on the original core.  The only
way it seems likely is if the new thread is started on the same core
that's already in fdl_init, and the new thread preempts the old, which
many would consider broken . . . but there are plenty of broken thread
implementations and it's hardly surprising that glibc has one.  Still,
it's a race and it did show up in regression tests a few times, so it
needs to be fixed.

Change-Id: Ifa5b0ae1ec111860f0d3f55a98aa2b8f2cef84ca
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/13674
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/xlators/experimental/fdl/src/fdl-tmpl.c b/xlators/experimental/fdl/src/fdl-tmpl.c
index 8fcc6a8d6ff..fdcfafbac31 100644
--- a/xlators/experimental/fdl/src/fdl-tmpl.c
+++ b/xlators/experimental/fdl/src/fdl-tmpl.c
@@ -417,12 +417,7 @@ fdl_init (xlator_t *this)
 
         GF_OPTION_INIT ("log-path", priv->log_dir, path, err);
 
-        if (pthread_create(&priv->worker,NULL,fdl_worker,this) != 0) {
-                gf_log (this->name, GF_LOG_ERROR,
-                        "failed to start fdl_worker");
-                goto err;
-        }
-
+        this->private = priv;
         /*
          * The rest of the fop table is automatically generated, so this is a
          * bit cleaner than messing with the generation to add a hand-written
@@ -430,7 +425,12 @@ fdl_init (xlator_t *this)
          */
         this->fops->ipc = fdl_ipc;
 
-        this->private = priv;
+        if (pthread_create(&priv->worker,NULL,fdl_worker,this) != 0) {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "failed to start fdl_worker");
+                goto err;
+        }
+
         return 0;
 
 err: