[knem-devel] "unexisting region cookie" error

Brice Goglin Brice.Goglin at inria.fr
Mon Jul 11 23:27:07 CEST 2011


Le 11/07/2011 23:19, bin wang a écrit :
> yeah, I forgot to use the run the cmd as root.
>
> I have one writer who will send its data to two readers.
>
> 1) On the writer side, I'm use the same memory buffer to register
> twice and get exactly the same cookie.
> [...]
>  Context 56119d42
>   Region 02f4c51c SingleUse
>   Region 02f4c51d SingleUse
>   Listed 2 regions

The cookies are not exactly the same here. Cookie values are a
combination of the above context + region values, so one bit of the
64bit cookie values should be different. If I remember correctly, the
bit should be the 33rd or 34th one of the 64bit values.

> 2) I send the cookie to the two readers. try to ask one reader reads
> first,
> [...]
>  Context 56119d42
>   Region 02f4c51c SingleUse
>   Listed 1 regions

The second cookie got removed because it had the singleuse flag and it
was used by the first process. If the next process thinks the cookies
are the same, it will read again from this now-unexisting cookie and get
an error because it doesn't exist anymore.

Brice

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