On Mon, Feb 27, 2012 at 6:29 PM, Aldy Hernandez <al...@redhat.com> wrote:
> On 02/27/12 11:02, Michael Matz wrote:
>>
>> Hi,
>>
>> On Mon, 27 Feb 2012, Aldy Hernandez wrote:
>>
>>>
>>>>> For that matter, didn't rth add a memory barrier at the beginning of
>>>>> transactions last week? That would mean that we can't hoist anything
>>>>> outside of a transaction anyhow. Or was it not a full memory barrier?
>>>>
>>>>
>>>> It's now a full memory barrier for all global memory and for local
>>>> statics
>>>> if their address is taken (and for automatic vars with their address
>>>> taken).
>>>> Do we need to be concerned about non-address-taken local statics?
>>>
>>>
>>> It is my understanding that non-address-taken local statics are not
>>> visible to other threads,
>>
>>
>> void f () { static int i; i++; }
>>
>> Running 'f' in different threads will expose the storage to 'i' to each of
>> them without taking its address :-/
>
>
> In that case, shouldn't we make transactions barriers for local statics as
> well, regardless of if their address was taken or not?
We don't have a convenient bit for this right now, but OTOH we assume
that the transaction may re-enter the function, and thus it should already
be a barrier for local statics. Unless the builtins have the "leaf" attribute
on them.
Richard.
