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From Joe Orton <jor...@redhat.com>
Subject Re: apr_shm_attach() and APR_EEXIST
Date Thu, 27 May 2004 14:03:06 GMT
On Wed, May 26, 2004 at 09:43:38PM +0530, Amit Athavale wrote:
> Graham Leggett wrote:
> 
> >Ok - what I would like to do is put information on what needs to be 
> >done in the error message, so that when mod_ldap starts and the shared 
> >memory goes pear shaped, the admin is given exact instructions on what 
> >to do to fix it, this removing your step 4 above, and hopefully also 
> >step 6. [1]
> >
> >Something like: "LDAP cache: shared memory segment could not be 
> >created due to problems with an unclean shutdown. Please run 'ipcrm -m 
> >XXXX' to fix this."
> >
> >How would I get the XXXX part? Is this returned anywhere? 
> 
> I don't think it is possible. APR does not pass back any information
> in case of error, other than error code itself. (and anyway XXX is shmid
> returned by shmget() which is failing in your case)

Agreed.  The answer is that the name-based shm interface is not useful;
always use anonymous shm by default and all the headaches go away.

I guess it could be made useful either by having apr_shm_create() remove
an existing shm segment with the given name then re-create it (as MM
does IIRC), or to add an apr_shm_remove() function which removes a
name-based shm segment as only APR knows how.

joe

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