Re: [Qemu-devel] [RFC v3 03/19] translate-all: add DEBUG_LOCKING asserts

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 23/06/16 20:14, Alex Bennée wrote:
> Sergey Fedorov <serge.fdrv@gmail.com> writes:
>
>> On 03/06/16 23:40, Alex Bennée wrote:
>>> diff --git a/translate-all.c b/translate-all.c
>>> index ec6fdbb..e3f44d9 100644
>>> --- a/translate-all.c
>>> +++ b/translate-all.c
>> (snip)
>>> @@ -60,6 +61,7 @@
>>>
>>>  /* #define DEBUG_TB_INVALIDATE */
>>>  /* #define DEBUG_TB_FLUSH */
>>> +/* #define DEBUG_LOCKING */
>> A bit of bikeshedding: have you considered naming it 'DEBUG_LOCKS'. How
>> does it sound for a native English speaker? :)
>>
>>>  /* make various TB consistency checks */
>>>  /* #define DEBUG_TB_CHECK */
>>>
>>> @@ -68,6 +70,28 @@
>>>  #undef DEBUG_TB_CHECK
>>>  #endif
>>>
>>> +/* Access to the various translations structures need to be serialised via locks
>>> + * for consistency. This is automatic for SoftMMU based system
>>> + * emulation due to its single threaded nature. In user-mode emulation
>>> + * access to the memory related structures are protected with the
>>> + * mmap_lock.
>>> + */
>>> +#ifdef DEBUG_LOCKING
>>> +#define DEBUG_MEM_LOCKS 1
>>> +#else
>>> +#define DEBUG_MEM_LOCKS 0
>>> +#endif
>>> +
>>> +#ifdef CONFIG_SOFTMMU
>>> +#define assert_memory_lock() do { /* nothing */ } while (0)
>>> +#else
>>> +#define assert_memory_lock() do {               \
>>> +        if (DEBUG_MEM_LOCKS) {                  \
>>> +            g_assert(have_mmap_lock());         \
>>> +        }                                       \
>>> +    } while (0)
>>> +#endif
>>> +
>> Why not simply:
>>
>> #if !defined(DEBUG_LOCKING) || defined(CONFIG_SOFTMMU)
>> #    define assert_memory_lock() do { /* nothing */ } while (0)
>> #else
>> #    define assert_memory_lock() g_assert(have_mmap_lock())
>> #endif
>>
>> One more nit: maybe it would be a bit more clear to name it after the
>> lock name, i.e. assert_mmap_lock(), or check_mmap_lock(), or
>> debug_mmap_lock() etc?
> Yes I can do it that way around. The if (FOO) form makes more sense for
> debug output to ensure the compiler checks format strings etc. The
> resulting code should be the same either way.

You are right, this is a good thing, I just missed it.

Thanks,
Sergey