• Stefan Hajnoczi's avatar
    coroutine: stop using AioContext in CoQueue · 02ffb504
    Stefan Hajnoczi authored
    qemu_co_queue_next(&queue) arranges that the next queued coroutine is
    run at a later point in time.  This deferred restart is useful because
    the caller may not want to transfer control yet.
    
    This behavior was implemented using QEMUBH in the past, which meant that
    CoQueue (and hence CoMutex and CoRwlock) had a dependency on the
    AioContext event loop.  This hidden dependency causes trouble when we
    move to a world with multiple event loops - now qemu_co_queue_next()
    needs to know which event loop to schedule the QEMUBH in.
    
    After pondering how to stash AioContext I realized the best solution is
    to not use AioContext at all.  This patch implements the deferred
    restart behavior purely in terms of coroutines and no longer uses
    QEMUBH.
    
    Here is how it works:
    
    Each Coroutine has a wakeup queue that starts out empty.  When
    qemu_co_queue_next() is called, the next coroutine is added to our
    wakeup queue.  The wakeup queue is processed when we yield or terminate.
    Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
    02ffb504
qemu-coroutine.c 2.87 KB