| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org>, Christophe Pettus <xof(at)thebuild(dot)com> |
| Subject: | Re: "stuck spinlock" |
| Date: | 2013-12-13 15:24:42 |
| Message-ID: | 20131213152442.GL29402@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2013-12-13 09:52:06 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > Tom, could this be caused by c357be2cd9434c70904d871d9b96828b31a50cc5?
> > Specifically the added CHECK_FOR_INTERRUPTS() in handle_sig_alarm()?
> > ISTM nothing is preventing us from jumping out of code holding a
> > spinlock?
>
> Hm ... what should stop it is that ImmediateInterruptOK wouldn't be
> set while we're messing with any spinlocks. Except that ProcessInterrupts
> doesn't check that gating condition :-(.
It really can't, right? Otherwise explicit CHECK_FOR_INTERRUPTS()s in
normal code wouldn't do much anymore since ImmediateInterruptOK is so
seldomly set. The control flow around signal handling always drives me
crazy.
> I think you're probably right:
> what should be in the interrupt handler is something like
> "if (ImmediateInterruptOK) CHECK_FOR_INTERRUPTS();"
Yea, that sounds right. Or just don't set process interrupts there, it
doesn't seem to be required for correctness?
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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