Re: [Qemu-devel] [PATCH] NVMe: Initial commit to add an NVM Express device

[Paolo Bonzini <pbonzini@redhat.com>]

Il 13/12/2012 10:12, Kevin Wolf ha scritto:
>>> 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?

Yes, that's the main problem.

Paolo