Re: [Qemu-devel] [RFC PATCH] fix select(2) race between main_loop_wait and qemu_aio_wait

[Jan Kiszka]

On 2012-03-05 18:39, Avi Kivity wrote:
> On 03/05/2012 04:30 PM, Jan Kiszka wrote:
>> On 2012-03-05 15:24, Avi Kivity wrote:
>>>> Long-term, I'd like to cut out certain file descriptors from the main
>>>> loop and process them completely in separate threads (for separate
>>>> locking, prioritization etc.). Dunno how NBD works, but maybe it should
>>>> be reworked like this already.
>>>
>>> Ideally qemu_set_fd_handler2() should be made thread local, and each
>>> device thread would run a copy of the main loop, just working on
>>> different data.
>>
>> qemu_set_fd_handler2 may not only be called over an iothread. Rather, we
>> need an object and associated lock that is related to the io-path (i.e.
>> frontend device + backend driver). That object has to be passed to
>> services like qemu_set_fd_handler2.
> 
> Not sure I like implicit lock-taking.  In particular, how does it
> interact with unregistering an fd_handler?

I wasn't suggesting implicit lock taking, just decoupling from our
infamous global lock. My point is that thread-local won't help here.

Jan

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