[PATCH 31/55] coroutine: Add qemu_co_mutex_assert_locked()

[Michael Roth]

From: Kevin Wolf <address@hidden>

Some functions require that the caller holds a certain CoMutex for them
to operate correctly. Add a function so that they can assert the lock is
really held.

Cc: address@hidden
Signed-off-by: Kevin Wolf <address@hidden>
Tested-by: Michael Weiser <address@hidden>
Reviewed-by: Michael Weiser <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Reviewed-by: Denis V. Lunev <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
(cherry picked from commit 944f3d5dd216fcd8cb007eddd4f82dced0a15b3d)
Signed-off-by: Michael Roth <address@hidden>
---
 include/qemu/coroutine.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index 9801e7f5a4..f4843b5f59 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -167,6 +167,21 @@ void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
  */
 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
 
+/**
+ * Assert that the current coroutine holds @mutex.
+ */
+static inline coroutine_fn void qemu_co_mutex_assert_locked(CoMutex *mutex)
+{
+    /*
+     * mutex->holder doesn't need any synchronisation if the assertion holds
+     * true because the mutex protects it. If it doesn't hold true, we still
+     * don't mind if another thread takes or releases mutex behind our back,
+     * because the condition will be false no matter whether we read NULL or
+     * the pointer for any other coroutine.
+     */
+    assert(atomic_read(&mutex->locked) &&
+           mutex->holder == qemu_coroutine_self());
+}
 
 /**
  * CoQueues are a mechanism to queue coroutines in order to continue executing
-- 
2.17.1