Merge remote-tracking branch 'remotes/famz/tags/block-and-testing-pull-request' into staging

# gpg: Signature made Mon 17 Jul 2017 04:47:05 BST
# gpg:                using RSA key 0xCA35624C6A9171C6
# gpg: Good signature from "Fam Zheng <famz@redhat.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 5003 7CB7 9706 0F76 F021  AD56 CA35 624C 6A91 71C6

* remotes/famz/tags/block-and-testing-pull-request:
  travis: add no-TCG build
  docker.py: Improve subprocess exit code handling
  docker.py: Drop infile parameter
  docker: Don't enable networking as a side-effect of DEBUG=1
  ssh: support I/O from any AioContext
  sheepdog: add queue_lock
  qed: protect table cache with CoMutex
  qed: introduce bdrv_qed_init_state
  block: invoke .bdrv_drain callback in coroutine context and from AioContext
  qed: move tail of qed_aio_write_main to qed_aio_write_{cow, alloc}
  vvfat: make it thread-safe
  vpc: make it thread-safe
  vdi: make it thread-safe
  coroutine-lock: add qemu_co_rwlock_downgrade and qemu_co_rwlock_upgrade
  qcow2: call CoQueue APIs under CoMutex

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index b44b5d55eb..846ff9167f 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -402,6 +402,21 @@ void qemu_co_rwlock_unlock(CoRwlock *lock)
     qemu_co_mutex_unlock(&lock->mutex);
 }
 
+void qemu_co_rwlock_downgrade(CoRwlock *lock)
+{
+    Coroutine *self = qemu_coroutine_self();
+
+    /* lock->mutex critical section started in qemu_co_rwlock_wrlock or
+     * qemu_co_rwlock_upgrade.
+     */
+    assert(lock->reader == 0);
+    lock->reader++;
+    qemu_co_mutex_unlock(&lock->mutex);
+
+    /* The rest of the read-side critical section is run without the mutex.  */
+    self->locks_held++;
+}
+
 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 {
     qemu_co_mutex_lock(&lock->mutex);
@@ -416,3 +431,23 @@ void qemu_co_rwlock_wrlock(CoRwlock *lock)
      * There is no need to update self->locks_held.
      */
 }
+
+void qemu_co_rwlock_upgrade(CoRwlock *lock)
+{
+    Coroutine *self = qemu_coroutine_self();
+
+    qemu_co_mutex_lock(&lock->mutex);
+    assert(lock->reader > 0);
+    lock->reader--;
+    lock->pending_writer++;
+    while (lock->reader) {
+        qemu_co_queue_wait(&lock->queue, &lock->mutex);
+    }
+    lock->pending_writer--;
+
+    /* The rest of the write-side critical section is run with
+     * the mutex taken, similar to qemu_co_rwlock_wrlock.  Do
+     * not account for the lock twice in self->locks_held.
+     */
+    self->locks_held--;
+}