Re: [PATCH] Document Linux's memory barriers [try #4]

[David Howells]

Sergei Organov <osv@xxxxxxxxx> wrote:

> "You can prevent an `asm' instruction from being deleted by writing the
> keyword `volatile' after the `asm'. [...]
> The `volatile' keyword indicates that the instruction has important
> side-effects.  GCC will not delete a volatile `asm' if it is reachable.
> (The instruction can still be deleted if GCC can prove that
> control-flow will never reach the location of the instruction.)  *Note
> that even a volatile `asm' instruction can be moved relative to other
> code, including across jump instructions.*"

Ummm... If "asm volatile" statements don't form compiler barriers, then how do
you specify a compiler barrier? Or is that what the "memory" bit in:

	#define barrier() __asm__ __volatile__("": : :"memory")

does?

David
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