On 5/12/20 4:43 PM, Kevin Wolf wrote:
> Coroutine functions that are entered through bdrv_run_co() are already
> safe to call from synchronous code in a different AioContext because
> bdrv_coroutine_enter() will schedule them in the context of the node.
>
> However, the coroutine fastpath still requires that we're already in the
> right AioContext when called in coroutine context.
>
> In order to make the behaviour more consistent and to make life a bit
> easier for callers, let's check the AioContext and automatically move
> the current coroutine around if we're not in the right context yet.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> ---
> block/io.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/block/io.c b/block/io.c
> index c1badaadc9..7808e8bdc0 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -895,8 +895,21 @@ static int bdrv_run_co(BlockDriverState *bs,
> CoroutineEntry *entry,
> void *opaque, int *ret)
> {
> if (qemu_in_coroutine()) {
> - /* Fast-path if already in coroutine context */
> + Coroutine *self = qemu_coroutine_self();
> + AioContext *bs_ctx = bdrv_get_aio_context(bs);
> + AioContext *co_ctx = qemu_coroutine_get_aio_context(self);
> +
> + if (bs_ctx != co_ctx) {
> + /* Move to the iothread of the node */
> + aio_co_schedule(bs_ctx, self);
> + qemu_coroutine_yield();
> + }
> entry(opaque);
> + if (bs_ctx != co_ctx) {
> + /* Move back to the original AioContext */
> + aio_co_schedule(bs_ctx, self);
shouldn't it use co_ctx here, as else it's just scheduled again on the one from
bs?
Looks OK for me besides that.
> + qemu_coroutine_yield();
> + }
> } else {
> Coroutine *co = qemu_coroutine_create(entry, opaque);
> *ret = NOT_DONE;
>
