[PULL 20/34] nbd/client-connection: use QEMU_LOCK_GUARD

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We don't update connect_thread_func() to use QEMU_LOCK_GUARD, as it
will get more complex critical sections logic in further commit, where
QEMU_LOCK_GUARD doesn't help.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-19-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/client-connection.c | 95 +++++++++++++++++++----------------------
 1 file changed, 43 insertions(+), 52 deletions(-)

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index f3b270d38cc8..eb5cae2eaea4 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -125,14 +125,14 @@ void nbd_client_connection_release(NBDClientConnection 
*conn)
         return;
     }

-    qemu_mutex_lock(&conn->mutex);
-    assert(!conn->detached);
-    if (conn->running) {
-        conn->detached = true;
-    } else {
-        do_free = true;
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        assert(!conn->detached);
+        if (conn->running) {
+            conn->detached = true;
+        } else {
+            do_free = true;
+        }
     }
-    qemu_mutex_unlock(&conn->mutex);

     if (do_free) {
         nbd_client_connection_do_free(conn);
@@ -150,62 +150,55 @@ void nbd_client_connection_release(NBDClientConnection 
*conn)
 QIOChannelSocket *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
 {
-    QIOChannelSocket *sioc = NULL;
     QemuThread thread;

-    qemu_mutex_lock(&conn->mutex);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        /*
+         * Don't call nbd_co_establish_connection() in several coroutines in
+         * parallel. Only one call at once is supported.
+         */
+        assert(!conn->wait_co);

-    /*
-     * Don't call nbd_co_establish_connection() in several coroutines in
-     * parallel. Only one call at once is supported.
-     */
-    assert(!conn->wait_co);
+        if (!conn->running) {
+            if (conn->sioc) {
+                /* Previous attempt finally succeeded in background */
+                return g_steal_pointer(&conn->sioc);
+            }

-    if (!conn->running) {
-        if (conn->sioc) {
-            /* Previous attempt finally succeeded in background */
-            sioc = g_steal_pointer(&conn->sioc);
-            qemu_mutex_unlock(&conn->mutex);
-
-            return sioc;
+            conn->running = true;
+            error_free(conn->err);
+            conn->err = NULL;
+            qemu_thread_create(&thread, "nbd-connect",
+                               connect_thread_func, conn, 
QEMU_THREAD_DETACHED);
         }

-        conn->running = true;
-        error_free(conn->err);
-        conn->err = NULL;
-        qemu_thread_create(&thread, "nbd-connect",
-                           connect_thread_func, conn, QEMU_THREAD_DETACHED);
+        conn->wait_co = qemu_coroutine_self();
     }

-    conn->wait_co = qemu_coroutine_self();
-
-    qemu_mutex_unlock(&conn->mutex);
-
     /*
      * We are going to wait for connect-thread finish, but
      * nbd_co_establish_connection_cancel() can interrupt.
      */
     qemu_coroutine_yield();

-    qemu_mutex_lock(&conn->mutex);
-
-    if (conn->running) {
-        /*
-         * The connection attempt was canceled and the coroutine resumed
-         * before the connection thread finished its job.  Report the
-         * attempt as failed, but leave the connection thread running,
-         * to reuse it for the next connection attempt.
-         */
-        error_setg(errp, "Connection attempt cancelled by other operation");
-    } else {
-        error_propagate(errp, conn->err);
-        conn->err = NULL;
-        sioc = g_steal_pointer(&conn->sioc);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        if (conn->running) {
+            /*
+             * The connection attempt was canceled and the coroutine resumed
+             * before the connection thread finished its job.  Report the
+             * attempt as failed, but leave the connection thread running,
+             * to reuse it for the next connection attempt.
+             */
+            error_setg(errp, "Connection attempt cancelled by other 
operation");
+            return NULL;
+        } else {
+            error_propagate(errp, conn->err);
+            conn->err = NULL;
+            return g_steal_pointer(&conn->sioc);
+        }
     }

-    qemu_mutex_unlock(&conn->mutex);
-
-    return sioc;
+    abort(); /* unreachable */
 }

 /*
@@ -220,11 +213,9 @@ void 
nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 {
     Coroutine *wait_co;

-    qemu_mutex_lock(&conn->mutex);
-
-    wait_co = g_steal_pointer(&conn->wait_co);
-
-    qemu_mutex_unlock(&conn->mutex);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        wait_co = g_steal_pointer(&conn->wait_co);
+    }

     if (wait_co) {
         aio_co_wake(wait_co);
-- 
2.31.1