features/changelog: Change barrier notification mechanism

The barrier notification mechanism was fd based and 'select'
was being used. 'select' breaks when number of fds opened
by brick process exceeds 1024. To avoid this and also
the maintainance of pipe between notify and 'changelog_rollover',
the pipe has been replaced with pthread condition signal
and timed wait mechanism.

Change-Id: I530ea90d9a06953f8b23b4e12d122872ee1925de
BUG: 1334314
Signed-off-by: Kotresh HR <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/14272
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: Aravinda VK <avishwan@redhat.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>

1 files changed, 38 insertions, 46 deletions

diff --git a/xlators/features/changelog/src/changelog-helpers.c b/xlators/features/changelog/src/changelog-helpers.c
index 6d3b99c6cdc..0cb68587e57 100644
--- a/xlators/features/changelog/src/changelog-helpers.c
+++ b/xlators/features/changelog/src/changelog-helpers.c
@@ -1259,15 +1259,10 @@ changelog_rollover (void *data)
 {
         int                     ret             = 0;
         xlator_t               *this            = NULL;
-        struct timeval          tv              = {0,};
+        struct timespec         tv              = {0,};
         changelog_log_data_t    cld             = {0,};
         changelog_time_slice_t *slice           = NULL;
         changelog_priv_t       *priv            = data;
-        int                     max_fd          = 0;
-        char                    buf[1]          = {0};
-        int                     len             = 0;
-
-        fd_set                  rset;
 
         this = priv->cr.this;
         slice = &priv->slice;
@@ -1275,48 +1270,42 @@ changelog_rollover (void *data)
         while (1) {
                 (void) pthread_testcancel();
 
-                tv.tv_sec  = priv->rollover_time;
-                tv.tv_usec = 0;
-                FD_ZERO(&rset);
-                FD_SET(priv->cr.rfd, &rset);
-                max_fd = priv->cr.rfd;
-                max_fd = max_fd + 1;
-
-               /* It seems there is a race between actual rollover and explicit
-                * rollover. But it is handled. If actual rollover is being
-                * done and the explicit rollover event comes, the event is
-                * not missed. The next select will immediately wakeup to
-                * handle explicit wakeup.
+                tv.tv_sec  = time (NULL) + priv->rollover_time;
+                tv.tv_nsec = 0;
+                ret = 0; /* Reset ret to zero */
+
+               /* The race between actual rollover and explicit rollover is
+                * handled. If actual rollover is being done and the
+                * explicit rollover event comes, the event is not missed.
+                * Since explicit rollover sets 'cr.notify' to true, this
+                * thread doesn't wait on 'pthread_cond_timedwait'.
                 */
+                pthread_cleanup_push (changelog_cleanup_free_mutex,
+                                      &priv->cr.lock);
+                pthread_mutex_lock (&priv->cr.lock);
+                {
+                        while (ret == 0 && !priv->cr.notify)
+                                ret = pthread_cond_timedwait (&priv->cr.cond,
+                                                              &priv->cr.lock,
+                                                              &tv);
+                        if (ret == 0)
+                                priv->cr.notify = _gf_false;
+                }
+                pthread_mutex_unlock (&priv->cr.lock);
+                pthread_cleanup_pop (0);
 
-                ret = select (max_fd, &rset, NULL, NULL, &tv);
-                if (ret == -1) {
-                        gf_msg (this->name, GF_LOG_ERROR, errno,
-                                CHANGELOG_MSG_SELECT_FAILED,
-                                "select failed");
-                        continue;
-                } else if (ret && FD_ISSET(priv->cr.rfd, &rset)) {
+                if (ret == 0) {
                         gf_msg (this->name, GF_LOG_INFO, 0,
                                 CHANGELOG_MSG_BARRIER_INFO,
-                                "Explicit wakeup of select on barrier notify");
-                        len = sys_read (priv->cr.rfd, buf, 1);
-                        if (len == 0) {
-                                gf_msg (this->name, GF_LOG_ERROR, errno,
-                                        CHANGELOG_MSG_READ_ERROR, "BUG: Got EOF"
-                                        " from reconfigure notification pipe");
-                                continue;
-                        }
-                        if (len < 0) {
-                                gf_msg (this->name, GF_LOG_ERROR, 0,
-                                        CHANGELOG_MSG_READ_ERROR,
-                                        "Failed to read wakeup data");
-                                continue;
-                        }
-                        /* Lock is not required as same thread is modifying.*/
+                                "Explicit wakeup on barrier notify");
                         priv->explicit_rollover = _gf_true;
-                } else {
-                        gf_msg_debug (this->name, 0,
-                                      "select wokeup on timeout");
+                } else if (ret && ret != ETIMEDOUT) {
+                        gf_msg (this->name, GF_LOG_ERROR, errno,
+                                CHANGELOG_MSG_SELECT_FAILED,
+                                "pthread_cond_timedwait failed");
+                        continue;
+                } else if (ret && ret == ETIMEDOUT) {
+                        gf_msg_debug (this->name, 0, "Wokeup on timeout");
                 }
 
                /* Reading curent_color without lock is fine here
@@ -1783,9 +1772,12 @@ changelog_barrier_notify (changelog_priv_t *priv, char *buf)
 {
         int ret = 0;
 
-        LOCK(&priv->lock);
-                ret = changelog_write (priv->cr_wfd, buf, 1);
-        UNLOCK(&priv->lock);
+        pthread_mutex_lock (&priv->cr.lock);
+        {
+                ret = pthread_cond_signal (&priv->cr.cond);
+                priv->cr.notify = _gf_true;
+        }
+        pthread_mutex_unlock (&priv->cr.lock);
         return ret;
 }