RE: [Infiniband-general] Getting an Infiniband access layer in theLinux kernel

[Perez-Gonzalez, Inaky]

> From: Tillier, Fabian
> ...
>
> Having atomic operations return a value allows one to do something like
> test for zero when decrementing an atomic variable such as a reference
> count, to determine whether final cleanup should proceed.  This removes
> the need for an actual spinlock protecting the reference count.  As you
> know, reading the value post-decrement does not guarantee that said
> value reflects the result of only that decrement operation.  It would be
> catastrophic if two threads checked the value of a reference count
> without proper synchronization - they could both end up running the
> cleanup code with undesired (and perhaps catastrophic) results.

atomic_dec_and_test() does just that (asm/atomic.h).

Iñaky Pérez-González -- Not speaking for Intel -- all opinions are my own (and my fault)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/