Re: [patch] futex requeueing feature, futex-requeue-2.5.69-D3

[Ulrich Drepper <drepper@redhat.com>]

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Rusty Russell wrote:

> 1) Overload the last futex arg (change from timeval * to void *),
>    don't add YA arg at the end.

It wasn't Ingo's idea.  I suggested it.  Overloading parameter types is
evil.  This isn't an issue anymore if the extension is implemented as a
new syscall which certainly is better.


> 2) Use __alignof__(u32) not sizeof(u32).  Sure, they're the same, but
>    you really mean __alignof__ here.

I would always use sizeof() in this situation.  alignof is a property
the compiler can potentially relax.  On x86 it could easily be defined
to 1 in case someone wants to save memory.  OK, not really useful for
x86, but some embedded archs might be in such a situation.  Using
sizeof() makes sure that the variable is always 4-byte aligned.  For
atomic operations this certainly is a good minimal requirement.

If you want to really correct you might have to introduce something like
atomic_alignof().

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