Re: [PATCH v6 00/33] block layer: split block APIs in global state and I/O

[Kevin Wolf]

Am 21.01.2022 um 18:05 hat Emanuele Giuseppe Esposito geschrieben:
> Each function in the GS API will have an assertion, checking
> that it is always running under BQL.
> I/O functions are instead thread safe (or so should be), meaning
> that they *can* run under BQL, but also in an iothread in another
> AioContext. Therefore they do not provide any assertion, and
> need to be audited manually to verify the correctness.

I wonder if we could actually do something to catch at least some kinds
of bugs. The first conclusion from thinking about it is that we probably
shouldn't open-code assert(qemu_in_main_thread()) everywhere, but have a
macro or inline function for each category to be called in each function.

So an IO_CODE() macro could increase a counter in the coroutine object
(that is decreased again at the end of the function with g_auto), and
then GLOBAL_STATE_CODE() could not only assert that we're holding the
BQL, but also that the counter is still 0, i.e. it is not (indirectly)
called by an I/O function.

We may want to enable this only in debug builds, but maybe still worth a
thought anyway?

Kevin