fs: dlm: requestqueue busy wait to event based wait

This patch changes the requestqueue busy waiting algorithm to use
atomic counter values and wait_event() to wait until the requestqueue is
empty. It will slightly reduce the number of holding ls_requestqueue_mutex
mutex.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 44a5c67..fd1c7a8 100644 (file)
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -626,6 +626,8 @@ struct dlm_ls {
        struct rw_semaphore     ls_in_recovery; /* block local requests */
        struct rw_semaphore     ls_recv_active; /* block dlm_recv */
        struct list_head        ls_requestqueue;/* queue remote requests */
+       atomic_t                ls_requestqueue_cnt;
+       wait_queue_head_t       ls_requestqueue_wait;
        struct mutex            ls_requestqueue_mutex;
        struct dlm_rcom         *ls_recover_buf;
        int                     ls_recover_nodeid; /* for debugging */

diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index b905665..4e41813 100644 (file)
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -564,6 +564,8 @@ static int new_lockspace(const char *name, const char *cluster,
        init_rwsem(&ls->ls_in_recovery);
        init_rwsem(&ls->ls_recv_active);
        INIT_LIST_HEAD(&ls->ls_requestqueue);
+       atomic_set(&ls->ls_requestqueue_cnt, 0);
+       init_waitqueue_head(&ls->ls_requestqueue_wait);
        mutex_init(&ls->ls_requestqueue_mutex);
        mutex_init(&ls->ls_clear_proc_locks);
 

diff --git a/fs/dlm/requestqueue.c b/fs/dlm/requestqueue.c
index e89e0ff..d0cf685 100644 (file)
--- a/fs/dlm/requestqueue.c
+++ b/fs/dlm/requestqueue.c
@@ -44,6 +44,7 @@ void dlm_add_requestqueue(struct dlm_ls *ls, int nodeid, struct dlm_message *ms)
        e->nodeid = nodeid;
        memcpy(&e->request, ms, ms->m_header.h_length);
 
+       atomic_inc(&ls->ls_requestqueue_cnt);
        mutex_lock(&ls->ls_requestqueue_mutex);
        list_add_tail(&e->list, &ls->ls_requestqueue);
        mutex_unlock(&ls->ls_requestqueue_mutex);
@@ -89,6 +90,8 @@ int dlm_process_requestqueue(struct dlm_ls *ls)
 
                mutex_lock(&ls->ls_requestqueue_mutex);
                list_del(&e->list);
+               if (atomic_dec_and_test(&ls->ls_requestqueue_cnt))
+                       wake_up(&ls->ls_requestqueue_wait);
                kfree(e);
 
                if (dlm_locking_stopped(ls)) {
@@ -115,14 +118,8 @@ int dlm_process_requestqueue(struct dlm_ls *ls)
 
 void dlm_wait_requestqueue(struct dlm_ls *ls)
 {
-       for (;;) {
-               mutex_lock(&ls->ls_requestqueue_mutex);
-               if (list_empty(&ls->ls_requestqueue))
-                       break;
-               mutex_unlock(&ls->ls_requestqueue_mutex);
-               schedule();
-       }
-       mutex_unlock(&ls->ls_requestqueue_mutex);
+       wait_event(ls->ls_requestqueue_wait,
+                  atomic_read(&ls->ls_requestqueue_cnt) == 0);
 }
 
 static int purge_request(struct dlm_ls *ls, struct dlm_message *ms, int nodeid)
@@ -161,6 +158,8 @@ void dlm_purge_requestqueue(struct dlm_ls *ls)
 
                if (purge_request(ls, ms, e->nodeid)) {
                        list_del(&e->list);
+                       if (atomic_dec_and_test(&ls->ls_requestqueue_cnt))
+                               wake_up(&ls->ls_requestqueue_wait);
                        kfree(e);
                }
        }