Re: [Xen-devel] [PATCH] i386 linux: make 32-bit PAE kernel work when built with newer gcc

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 14.03.06 11:09:29 >>>
>
>On 13 Mar 2006, at 16:40, Jan Beulich wrote:
>
>> The compiler isn't required to order the two stores 
>> ptep_get_and_clear_full() in any particular way, and we saw cases
>> where the upper 32 bits get stored before the lower ones, which causes 
>> the access to fail (page-fault propagated out of
>> Xen).
>
>Won't this need a barrier() (compile barrier) between the updates of 
>low and high portions?

No, I can't see why. The compiler isn't permitted to re-order separate writes 
across
sequence points (which is different from a single 64-bit write, where the 
compiler is
only expected to carry out the full 64-bit write prior to the next sequence 
point, but
nothing requires it to do this in any particular order).

Jan

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