Re: bug in futex.2, FUTEX_CMP_REQUEUE

["Jₑₙₛ Gustedt" <jens.gustedt@inria.fr>]

Hello Carlos,

On Tue, 27 May 2025 08:42:27 -0400, Carlos O'Donell wrote:

> Suggest:
> 
> (Specifying val as INT_MAX is not useful, because it would make the
>   FUTEX_CMP_REQUEUE  operation  equivalent  to  FUTEX_WAKE.)

That is not true because `val3` is checked for the first and not the
second, so they are not equivalent. And indeed `val` as `INT_MAX` is
usefull, because it provides a wake up of everybody with an additional
check of `val3`.

> Suggest:
> 
> (Specifying val2 as 0 is not useful, because it may make the
>   FUTEX_CMP_REQUEUE operation equivalent to FUTEX_WAKE depending
>   on val and val3.)

I think that specifying `val2` as `0` is in fact useful because it
provides a wake operation that additionally checks for `val3`. (and
does no requeing)


Thanks
Jₑₙₛ


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