Am 13.12.2012 01:13, schrieb Busch, Keith: > On Mon, Dec 10, 2012 at 7:11 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: >> Quick pointers to get started on Kevin's suggestion: >> >> bdrv_aio_readv(), bdrv_aio_writev(), bdrv_aio_flush(), and >> bdrv_aio_discard() provide the block device operations that emulated >> storage controllers use. > > There seems to be an issue with the bdrv_aio_[readv/writev] routines. I added > some additional tracing in the block and coroutine code, and well, long story > short, the coroutine "bdrv_co_io_em" needs to call "qemu_coroutine_yield" > before his aio callback "bdrv_co_io_em_complete" invokes > "qemu_coroutine_enter". It does not always win this race in my experiments, > and qemu aborts with a recursive re-entry error. I don't know this coroutine > code well enough to propose a fix -- I'd say maybe use locks but I think that > defeats the purpose of using coroutines if I understand them correctly?
The block layer, like most other qemu functions, is supposed to run under the qemu_global_mutex (also called BQL). Do you call into it from a different thread that doesn't take this lock? Kevin
