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Re: OSDL DBT-2 w/ PostgreSQL 7.3.4 and 7.4beta5

From: Mark Wong <markw(at)osdl(dot)org>
To: Manfred Spraul <manfred(at)colorfullife(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org,osdldbt-general(at)lists(dot)sourceforge(dot)net
Subject: Re: OSDL DBT-2 w/ PostgreSQL 7.3.4 and 7.4beta5
Date: 2003-11-01 19:19:55
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Sat, Nov 01, 2003 at 07:27:01PM +0100, Manfred Spraul wrote:
> Tom Lane wrote:
> >Manfred Spraul <manfred(at)colorfullife(dot)com> writes:
> >  
> >
> >>Is that really necessary?
> >>    
> >>
> >
> >Unfortunately, yes.  libpq can't change the global setting of SIGPIPE
> >without breaking the surrounding application, but we don't want to crash
> >the app if the server connection has disappeared, either.  So we have to
> >set the SIGPIPE handler and then restore it around every send().
> >  
> >
> Ok. Ahm. No, wait. libpq is multi-threaded, right?
> signal handlers are a process property, not a thread property - that 
> code is broken for multi-threaded apps.
> At least that's how I understand the opengroup man page, and a quick 
> google confirmed that:
> I haven't found a reliable thread-safe approach yet:
> My first idea was block with pthread_sigmask, after send check if 
> pending with sigpending, and then delete with sigwait, and restore 
> blocked state. But that breaks if SIGPIPE is blocked and a signal is 
> already pending: there is no way to remove our additional SIGPIPE. I 
> don't see how we can avoid destroying the realtime signal info.
> Mark: Is your dbt2 testapp multithreaded? I don't see the signal 
> functions near the top in the profiles on the osdl website.

Yeah, my dbt2 applications are multithreaded.


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Next:From: Tom LaneDate: 2003-11-01 19:20:46
Subject: Avoiding SIGPIPE (was Re: OSDL DBT-2 w/ PostgreSQL 7.3.4 and 7.4beta5)
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Subject: Re: OSDL DBT-2 w/ PostgreSQL 7.3.4 and 7.4beta5

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