virtiofsd: Kill threads when queues are stopped

Kill the threads we've started when the queues get stopped.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
With improvements by:
Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

tools/virtiofsd/fuse_virtio.c

@@ -41,6 +41,7 @@ struct fv_QueueInfo {
     /* Our queue index, corresponds to array position */
     int qidx;
     int kick_fd;
+    int kill_fd; /* For killing the thread */
 
     /* The element for the command currently being processed */
     VuVirtqElement *qe;
@@ -412,14 +413,17 @@ static void *fv_queue_thread(void *opaque)
     fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
              qi->qidx, qi->kick_fd);
     while (1) {
-        struct pollfd pf[1];
+        struct pollfd pf[2];
         pf[0].fd = qi->kick_fd;
         pf[0].events = POLLIN;
         pf[0].revents = 0;
+        pf[1].fd = qi->kill_fd;
+        pf[1].events = POLLIN;
+        pf[1].revents = 0;
 
         fuse_log(FUSE_LOG_DEBUG, "%s: Waiting for Queue %d event\n", __func__,
                  qi->qidx);
-        int poll_res = ppoll(pf, 1, NULL, NULL);
+        int poll_res = ppoll(pf, 2, NULL, NULL);
 
         if (poll_res == -1) {
             if (errno == EINTR) {
@@ -430,12 +434,23 @@ static void *fv_queue_thread(void *opaque)
             fuse_log(FUSE_LOG_ERR, "fv_queue_thread ppoll: %m\n");
             break;
         }
-        assert(poll_res == 1);
+        assert(poll_res >= 1);
         if (pf[0].revents & (POLLERR | POLLHUP | POLLNVAL)) {
             fuse_log(FUSE_LOG_ERR, "%s: Unexpected poll revents %x Queue %d\n",
                      __func__, pf[0].revents, qi->qidx);
             break;
         }
+        if (pf[1].revents & (POLLERR | POLLHUP | POLLNVAL)) {
+            fuse_log(FUSE_LOG_ERR,
+                     "%s: Unexpected poll revents %x Queue %d killfd\n",
+                     __func__, pf[1].revents, qi->qidx);
+            break;
+        }
+        if (pf[1].revents) {
+            fuse_log(FUSE_LOG_INFO, "%s: kill event on queue %d - quitting\n",
+                     __func__, qi->qidx);
+            break;
+        }
         assert(pf[0].revents & POLLIN);
         fuse_log(FUSE_LOG_DEBUG, "%s: Got queue event on Queue %d\n", __func__,
                  qi->qidx);
@@ -589,6 +604,28 @@ out:
     return NULL;
 }
 
+static void fv_queue_cleanup_thread(struct fv_VuDev *vud, int qidx)
+{
+    int ret;
+    struct fv_QueueInfo *ourqi;
+
+    assert(qidx < vud->nqueues);
+    ourqi = vud->qi[qidx];
+
+    /* Kill the thread */
+    if (eventfd_write(ourqi->kill_fd, 1)) {
+        fuse_log(FUSE_LOG_ERR, "Eventfd_write for queue %d: %s\n",
+                 qidx, strerror(errno));
+    }
+    ret = pthread_join(ourqi->thread, NULL);
+    if (ret) {
+        fuse_log(FUSE_LOG_ERR, "%s: Failed to join thread idx %d err %d\n",
+                 __func__, qidx, ret);
+    }
+    close(ourqi->kill_fd);
+    ourqi->kick_fd = -1;
+}
+
 /* Callback from libvhost-user on start or stop of a queue */
 static void fv_queue_set_started(VuDev *dev, int qidx, bool started)
 {
@@ -633,16 +670,16 @@ static void fv_queue_set_started(VuDev *dev, int qidx, bool started)
         }
         ourqi = vud->qi[qidx];
         ourqi->kick_fd = dev->vq[qidx].kick_fd;
+
+        ourqi->kill_fd = eventfd(0, EFD_CLOEXEC | EFD_SEMAPHORE);
+        assert(ourqi->kill_fd != -1);
         if (pthread_create(&ourqi->thread, NULL, fv_queue_thread, ourqi)) {
             fuse_log(FUSE_LOG_ERR, "%s: Failed to create thread for queue %d\n",
                      __func__, qidx);
             assert(0);
         }
     } else {
-        /* TODO: Kill the thread */
+        fv_queue_cleanup_thread(vud, qidx);
-        assert(qidx < vud->nqueues);
-        ourqi = vud->qi[qidx];
-        ourqi->kick_fd = -1;
     }
 }