Re: [libitm] Minor changes to libitm.h

[Patrick Marlier <patrick dot marlier at gmail dot com>]

On 01/24/2012 07:32 PM, Torvald Riegel wrote:
> > * Remove ITM_REGPARM from _ITM_beginTransaction since on x86-32, a
> > >  variadic function ignores regparm.
> > >  * Add ITM_PURE to _ITM_addUserCommitAction and _ITM_addUserUndoAction to
> > >  be usable inside transactions.
> Those should be called from transaction_pure code only, or from wrapper
> functions linked to using transaction_wrapper.  Thus, they don't need to
> be pure.  Alternatively, why should they be?

I though it was also allowed to be called inside transaction_safe code. 
This way, the developer has some callbacks on transactions events.
example:

void ucommit(void *arg)
{
  printf("Committed. now we can do undoable action (as printf) or ...\n");
}

__transaction_atomic {
  _ITM_addUserCommitAction(ucommit, _ITM_noTransactionId, NULL);
  ...
}

I read the ABI and right they seem to focus on the case of tm_wrap. In 
fact, I found those calls quite convenient sometimes but definitely not 
a problem for me.

Note that GCC does not annotate wrapped function automatically as 
transaction_pure. So the wrapper has to be transaction_pure too. I don't 
know if we should consider as a bug (Intel STM compiler adds the 
transaction_pure attribute automatically) or a feature of GCC.
In fact, I found this also quite cool to be able to propose an 
alternative and transactified function when used in transaction.

Thanks.
--
Patrick.