core: make the per glusterfs_ctx_t timer-wheel refcounted

xlators can use a 'global' timer-wheel for scheduling events. This
timer-wheel is managed per glusterfs_ctx_t, but does not need to be
allocated for every graph. When an xlator wants to use the timer-wheel,
it will be instanciated on demand, and provided to xlators that request
it later on.

By adding a reference counter to the glusterfs_ctx_t for the
timer-wheel, the threads and structures can be cleaned up when the last
xlator does not have a need for it anymore. In general, the xlators
request the timer-wheel in init(), and they should return it in fini().

Because the timer-wheel is managed per glusterfs_ctx_t, the functions
can be added to ctx.c and do not need to live in their very minimal
tw.[ch] files.


>Reported-by: Poornima G <pgurusid@redhat.com>
>Signed-off-by: Niels de Vos <ndevos@redhat.com>
>Reviewed-on: https://review.gluster.org/17068
>NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
>CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
>Smoke: Gluster Build System <jenkins@build.gluster.org>
>Reviewed-by: Amar Tumballi <amarts@redhat.com>
>Reviewed-by: Zhou Zhengping <johnzzpcrystal@gmail.com>
>Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
>(cherry picked from commit 73fcf3a874b2049da31d01b8363d1ac85c9488c2)

Change-Id: I19d225b39aaa272d9005ba7adc3104c3764f1572
BUG: 1450267
Reviewed-on: https://review.gluster.org/17262
Tested-by: Poornima G <pgurusid@redhat.com>
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: Niels de Vos <ndevos@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/glusterfsd/src/glusterfsd.c b/glusterfsd/src/glusterfsd.c
index cb92cbee867..bd10dff8430 100644
--- a/glusterfsd/src/glusterfsd.c
+++ b/glusterfsd/src/glusterfsd.c
@@ -80,7 +80,6 @@
 #include "exports.h"
 
 #include "daemon.h"
-#include "tw.h"
 
 
 /* using argp for command line parsing */
@@ -2510,9 +2509,10 @@ main (int argc, char *argv[])
 
         /* do this _after_ daemonize() */
         if (cmd->global_timer_wheel) {
-                ret = glusterfs_global_timer_wheel_init (ctx);
-                if (ret)
+                if (!glusterfs_ctx_tw_get (ctx)) {
+                        ret = -1;
                         goto out;
+                }
         }
 
         ret = glusterfs_volumes_init (ctx);