Horton

Re: Sync Rep v17

Andres Freund <andres@anarazel.de>

View thread
From: Andres Freund <andres@anarazel.de>
To: pgsql-hackers@postgresql.org
Cc: Marti Raudsepp <marti@juffo.org>, Fujii Masao <masao.fujii@gmail.com>, Simon Riggs <simon@2ndquadrant.com>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, Daniel Farina <daniel@heroku.com>
Date: 2011-02-22T10:09:48Z
Lists: pgsql-hackers 
On Tuesday 22 February 2011 09:59:21 Marti Raudsepp wrote:
> On Tue, Feb 22, 2011 at 07:38, Fujii Masao <masao.fujii@gmail.com> wrote:
> > +       SpinLockAcquire(&WalSndCtl->ctlmutex);
> > +       result = WalSndCtl->sync_rep_service_available;
> > +       SpinLockRelease(&WalSndCtl->ctlmutex);
> > 
> > volatile pointer needs to be used to prevent code rearrangement.
> 
> I don't think that's necessary. Spinlock functions already prevent
> reordering using __asm__ __volatile__
> 
> Otherwise, surely they would be utterly broken?
Its not the spinlock thats the problem but that "result" may be already loaded 
into a register. Thats not prohibited by __asm__ __volatile__.

Andres