Re: [PATCH-for-8.0] coroutine: Add missing <qemu/atomic.h> include

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> On 14/12/22 08:58, Markus Armbruster wrote:
>> Philippe Mathieu-Daudé <philmd@linaro.org> writes:
>> 
>>> qemu_co_mutex_assert_locked() calls qatomic_read(), which
>>> is declared in <qemu/atomic.h>. This fixes when refactoring:
>>>
>>>    In file included from include/qemu/osdep.h:113,
>>>                     from ../../util/error-report.c:13:
>>>    include/qemu/coroutine.h: In function 'qemu_co_mutex_assert_locked':
>>>    include/qemu/coroutine.h:182:12: error: implicit declaration of function 'qatomic_read' [-Werror=implicit-function-declaration]
>>>      182 |     assert(qatomic_read(&mutex->locked) &&
>>>          |            ^~~~~~~~~~~~
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>>> ---
>>>   include/qemu/coroutine.h | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
>>> index 89650a2d7f..1750c30d8e 100644
>>> --- a/include/qemu/coroutine.h
>>> +++ b/include/qemu/coroutine.h
>>> @@ -17,6 +17,7 @@
>>>     #include "qemu/queue.h"
>>>   #include "qemu/timer.h"
>>> +#include "qemu/atomic.h"
>>>     /**
>>>    * Coroutines are a mechanism for stack switching and can be used for
>> I think this papers over the actual problem.
>> Compiling qemu/coroutine.h by itself succeeds for me.  Printing headers
>> with -H shows:
>>      [osdep.h and everything it includes elided...]
>>      . ../include/qemu/coroutine.h
>>      .. /work/armbru/qemu/include/qemu/queue.h
>>      .. /work/armbru/qemu/include/qemu/timer.h
>>      ... /work/armbru/qemu/include/qemu/bitops.h
>>      .... /work/armbru/qemu/include/qemu/host-utils.h
>>      ..... /work/armbru/qemu/include/qemu/bswap.h
>>      ...... /usr/include/byteswap.h
>>      ....... /usr/include/bits/byteswap.h
>>      ..... /work/armbru/qemu/include/qemu/int128.h
>>      .... /work/armbru/qemu/include/qemu/atomic.h
>>      [more...]
>> So, qemu/coroutine.h *already* includes qemu/atomic.h, via qemu/timer.h
>> and qemu/bitops.h.
>
> Well I'm not sure this implicit dependency is correct, since "coroutine.h" explicitly access a function declared in "atomic.h";
> if I want to modify "qemu/timer.h" or "qemu/bitops.h" I'm back to
> this very patch.

We have a rule "every header should include everything it needs".  We
don't have a rule "every header should include everything it needs
directly".

Yes, this means that when you drop includes from a header, you may have
to add them back elsewhere.

>> I suspect the actual problem is an inclusion loop: qemu/coroutine.h and
>> qemu/lockable.h include each other.  See my
>>      Subject: [PATCH 4/4] coroutine: Break inclusion loop
>>      Message-Id: <20221208142306.2642640-5-armbru@redhat.com>
>> and Paolo's review.
>
> So I guess I'll wait your series to get merged and see what happens
> when I rebase my work on yours.

Makes sense to me.