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.

Change-Id: I19d225b39aaa272d9005ba7adc3104c3764f1572
BUG: 1442788
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>

1 files changed, 12 insertions, 6 deletions

diff --git a/libglusterfs/src/glusterfs.h b/libglusterfs/src/glusterfs.h
index 4d5ca839cd3..839a1d47d2a 100644
--- a/libglusterfs/src/glusterfs.h
+++ b/libglusterfs/src/glusterfs.h
@@ -36,6 +36,7 @@
 #include "logging.h"
 #include "lkowner.h"
 #include "compat-uuid.h"
+#include "refcount.h"
 
 #define GF_YES 1
 #define GF_NO  0
@@ -438,6 +439,12 @@ typedef enum {
 
 struct tvec_base;
 
+/* reference counting for the global (per ctx) timer-wheel */
+struct gf_ctx_tw {
+        GF_REF_DECL;
+        struct tvec_base *timer_wheel; /* global timer-wheel instance */
+};
+
 struct _glusterfs_ctx {
         cmd_args_t          cmd_args;
         char               *process_uuid;
@@ -506,14 +513,13 @@ struct _glusterfs_ctx {
          */
         mgmt_ssl_t          secure_srvr;
         /* Buffer to 'save' backtrace even under OOM-kill like situations*/
-        char btbuf[GF_BACKTRACE_LEN];
+        char                btbuf[GF_BACKTRACE_LEN];
 
-        pthread_mutex_t notify_lock;
-        pthread_cond_t notify_cond;
-        int notifying;
-
-        struct tvec_base *timer_wheel; /* global timer-wheel instance */
+        pthread_mutex_t     notify_lock;
+        pthread_cond_t      notify_cond;
+        int                 notifying;
 
+        struct gf_ctx_tw   *tw; /* refcounted timer_wheel */
 };
 typedef struct _glusterfs_ctx glusterfs_ctx_t;