[PATCH, libstdc++] Improve slightly __cxa_guard_acquire

[Benjamin De Kosnik]

On Thu, 30 Aug 2012 12:48:34 +0200
Thiago Macieira <thiago.macieira@intel.com> wrote:

> Hello
> 
> The attached patch is a simple improvement to make a thread that
> failed to set the waiting bit to exit the function earlier, if it
> detects that another thread has successfully finished initialising.
> It matches the CAS code from a few lines above.
> 
> The change from RELAXED to ACQUIRE is noted in the previous patch
> I've just sent.

I like this, but want

// make a thread that failed to set the waiting bit to exit the function
// earlier, if it detects that another thread has successfully finished
// initialising

added as a comment in the

if (expected == pending_bit)

branch. 

I would like to put this in trunk + comment and give it 2-3 days at
least before 4.7 branch.

-benjamin