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>"
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# 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, 18 insertions, 0 deletions

diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index a4509bd977..9aff9a735e 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -229,6 +229,24 @@ void qemu_co_rwlock_init(CoRwlock *lock);
 void qemu_co_rwlock_rdlock(CoRwlock *lock);
 
 /**
+ * Write Locks the CoRwlock from a reader.  This is a bit more efficient than
+ * @qemu_co_rwlock_unlock followed by a separate @qemu_co_rwlock_wrlock.
+ * However, if the lock cannot be upgraded immediately, control is transferred
+ * to the caller of the current coroutine.  Also, @qemu_co_rwlock_upgrade
+ * only overrides CoRwlock fairness if there are no concurrent readers, so
+ * another writer might run while @qemu_co_rwlock_upgrade blocks.
+ */
+void qemu_co_rwlock_upgrade(CoRwlock *lock);
+
+/**
+ * Downgrades a write-side critical section to a reader.  Downgrading with
+ * @qemu_co_rwlock_downgrade never blocks, unlike @qemu_co_rwlock_unlock
+ * followed by @qemu_co_rwlock_rdlock.  This makes it more efficient, but
+ * may also sometimes be necessary for correctness.
+ */
+void qemu_co_rwlock_downgrade(CoRwlock *lock);
+
+/**
  * Write Locks the mutex. If the lock cannot be taken immediately because
  * of a parallel reader, control is transferred to the caller of the current
  * coroutine.