Re: GCC proposal for "@" asm constraint

From: Linus Torvalds (torvalds@transmeta.com)
Date: Fri Sep 22 2000 - 12:35:16 EST


On Fri, 22 Sep 2000, Andrea Arcangeli wrote:
>
> This patch fixes the spinlock problems in read_lock/write_lock and also some
> alpha SMP race where clear_bit isn't enforcing a memory barrier

Why would clear_bit() be a memory barrier?

Anything that expects clear_bit() to be a memory barrier should be fixed.

Anything that wants a spinlock should use the spinlocks. Not the bit ops.
They are atomic, but they are not memory barriers.

                        Linus

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