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Re: [COMMITTERS] pgsql: Fix race condition in multixact code: it's possible

This is a discussion on Re: [COMMITTERS] pgsql: Fix race condition in multixact code: it's possible within the Pgsql Patches forums, part of the PostgreSQL category; --> Does this need to be backpatched? --------------------------------------------------------------------------- Tom Lane wrote: > Log Message: > ----------- > Fix race condition ...


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  #1 (permalink)  
Old 04-18-2008, 01:00 AM
Bruce Momjian
 
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Default Re: [COMMITTERS] pgsql: Fix race condition in multixact code: it's possible


Does this need to be backpatched?

---------------------------------------------------------------------------

Tom Lane wrote:
> Log Message:
> -----------
> Fix race condition in multixact code: it's possible to try to read a
> multixact's starting offset before the offset has been stored into the
> SLRU file. A simple fix would be to hold the MultiXactGenLock until the
> offset has been stored, but that looks like a big concurrency hit. Instead
> rely on knowledge that unset offsets will be zero, and loop when we see
> a zero. This requires a little extra hacking to ensure that zero is never
> a valid value for the offset. Problem reported by Matteo Beccati, fix
> ideas from Martijn van Oosterhout, Alvaro Herrera, and Tom Lane.
>
> Modified Files:
> --------------
> pgsql/src/backend/access/transam:
> multixact.c (r1.9 -> r1.10)
> (http://developer.postgresql.org/cvsw...r1=1.9&r2=1.10)
>
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  #2 (permalink)  
Old 04-18-2008, 01:00 AM
Tom Lane
 
Posts: n/a
Default Re: [COMMITTERS] pgsql: Fix race condition in multixact code: it's possible to try to

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Does this need to be backpatched?


No.

regards, tom lane

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