@@ -629,6 +629,9 @@ void aio_co_schedule(AioContext *ctx, Coroutine *co);
*
* Move the currently running coroutine to new_ctx. If the coroutine is already
* running in new_ctx, do nothing.
+ *
+ * Note that this function cannot reschedule from iohandler_ctx to
+ * qemu_aio_context.
*/
void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx);
@@ -661,6 +664,9 @@ void aio_co_enter(AioContext *ctx, Coroutine *co);
* If called from an IOThread this will be the IOThread's AioContext. If
* called from the main thread or with the "big QEMU lock" taken it
* will be the main loop AioContext.
+ *
+ * Note that the return value is never the main loop's iohandler_ctx and the
+ * return value is the main loop AioContext instead.
*/
AioContext *qemu_get_current_aio_context(void);
The main loop has two AioContexts: qemu_aio_context and iohandler_ctx. The main loop runs them both, but nested aio_poll() calls on qemu_aio_context exclude iohandler_ctx. Which one should qemu_get_current_aio_context() return when called from the main loop? Document that it's always qemu_aio_context. This has subtle effects on functions that use qemu_get_current_aio_context(). For example, aio_co_reschedule_self() does not work when moving from iohandler_ctx to qemu_aio_context because qemu_get_current_aio_context() does not differentiate these two AioContexts. Document this in order to reduce the chance of future bugs. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- include/block/aio.h | 6 ++++++ 1 file changed, 6 insertions(+)