Re: [PATCH] blkdebug: ignore invalid rules in non-coroutine context

[Paolo Bonzini]

On 10/13/22 12:56, Markus Armbruster wrote:
> rule_check() is called from blkdebug_co_preadv(), blkdebug_co_pwritev(),
> blkdebug_co_pwrite_zeroes(), blkdebug_co_pdiscard(),
> blkdebug_co_block_status() (all marked coroutine_fn), and
> blkdebug_co_flush() (which looks like it should be marked coroutine_fn).

Yes (separate patch sent, 
20221013123711.620631-11-pbonzini@redhat.com/T/#u">https://lore.kernel.org/qemu-devel/20221013123711.620631-11-pbonzini@redhat.com/T/#u).

> Ignorant question: how could it be called outside coroutine context?

You're right, only blkdebug_debug_event() can be called outside 
coroutine context.  I confused process_rule() (called by 
blkdebug_debug_event(), both inside and outside coroutine context) with 
rule_check() (called in coroutine context).

> Also, code smell: reporting an error without taking an error path.  But
> let's worry about that only after I understand the problem you're trying
> to fix.

Unfortunately there's no way to know in advance if an event will be 
called inside vs. outside a coroutine.  I can keep the abort() if you 
think it's preferrable, so what you get is still a crash but with a 
nicer error message.  Since this is debugging code either solution has 
pros and cons.

Paolo