| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org |
| Cc: | Marti Raudsepp <marti(at)juffo(dot)org>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Daniel Farina <daniel(at)heroku(dot)com> |
| Subject: | Re: Sync Rep v17 |
| Date: | 2011-02-22 10:09:48 |
| Message-ID: | 201102221109.49130.andres@anarazel.de |
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| 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(dot)fujii(at)gmail(dot)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
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