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The coroutine files are currently referenced by the block-obj-y
variable. The coroutine functionality though is already used by
more than just the block code. eg migration code uses coroutine
yield. In the future the I/O channel code will also use the
coroutine yield functionality. Since the coroutine code is nicely
self-contained it can be easily built as part of the libqemuutil.a
library, making it widely available.
The headers are also moved into include/qemu, instead of the
include/block directory, since they are now part of the util
codebase, and the impl was never in the block/ directory
either.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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qemu_coroutine_enter() is now the only user of coroutine_swap(). Both
functions are short, so inline it.
Also, using COROUTINE_YIELD is now even more confusing because this code
is never called during qemu_coroutine_yield() any more. In fact, this
value is never read back, so we can just introduce a new COROUTINE_ENTER
which documents the purpose of the task switch better.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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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: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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