Re: [PATCH RFC 1/1] futex: Create set_robust_list2

[Arnd Bergmann]

On Thu, Oct 24, 2024, at 19:55, André Almeida wrote:
> Em 24/10/2024 15:03, André Almeida escreveu:
>> Em 24/10/2024 12:57, Arnd Bergmann escreveu:
>>> On Thu, Oct 24, 2024, at 14:57, André Almeida wrote:
>>>> This new syscall allows to set multiple list to the same process. There
>>>> are two list types: 32 and 64 bit lists.
>>> Assuming we want them to behave the same way, did you intend
>>> ROBUST_LIST_64BIT to refer to 64-bit pointers on 32-bit
>>> tasks, or should they use normal word-size pointers?
>> 
>> Oh right, I haven't covered that indeed. I think I would need to have 
>> something like:
>> 
>> static void exit_robust_list_64()
>> static void exit_robust_list_32()
>> 
>> And then each function would use explicit sizes for pointers. Also, I 
>> would rewrite the conditions to make that every combination of 64/32bit 
>> kernel/app calls the appropriated function.
>
> Something like this:
>
> #ifdef CONFIG_64BIT
> 	if (unlikely(tsk->robust_list)) {
> 		exit_robust_list_64bit(tsk, tsk->robust_list);
> 		tsk->robust_list = NULL;
> 	}
> #else
> 	if (unlikely(tsk->robust_list)) {
> 		exit_robust_list_32bit(tsk, tsk->robust_list);
> 		tsk->robust_list = NULL;
> 	}
> #endif
>
> #ifdef CONFIG_COMPAT
> 	if (unlikely(tsk->compat_robust_list)) {
> 		exit_robust_32bit(tsk, tsk->compat_robust_list);
> 		tsk->compat_robust_list = NULL;
> 	}
> #endif

This should work, but I wonder if it ends up simpler to
instead have tsk->robust_list64 and tsk->robust_list32
entries and just put the #ifdef CONFIG_64BIT around the code
accessing robust_list64.

     Arnd