Re: sequence lock in Linux

From: H. Peter Anvin
Date: Fri Jun 11 2010 - 18:41:15 EST

On 06/11/2010 03:04 PM, Paul E. McKenney wrote:
> On Fri, Jun 11, 2010 at 02:38:59PM -0700, H. Peter Anvin wrote:
>> On 06/11/2010 02:36 PM, Paul E. McKenney wrote:
>>> Memory barriers in the sequence-lock code prevent this, assuming, as
>>> you point out, that memory clobber works (but if it doesn't, it should
>>> be fixed):
>> The constness is my main concern. It's not clear to me that "memory" is
>> meant to imply that const memory areas without volatile can be clobbered.
> Ah! I was assuming that gcc treated "memory" as it would an call to
> a function in some other compilation unit. In that case, the compiler
> could not count on the "const" on the argument, given the possibility
> that the called function might gain a reference to the same memory
> locations in a non-const manner, right?
> Thanx, Paul



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