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Posted to dev@httpd.apache.org by Stefan Eissing <st...@greenbytes.de> on 2019/05/09 09:01:32 UTC

eor bucket

Could someone help me to check my understanding of the eor bucket implementation?

If an eor bucket is ever copied, there are 2 buckets with their b->data pointing to the request_rec. Since this is local to the bucket, destroying these 2 will call apr_pool_destroy() twice on the pool. Correct?

-Stefan

Re: eor bucket

Posted by Stefan Eissing <st...@greenbytes.de>.


> Am 09.05.2019 um 11:28 schrieb Yann Ylavic <yl...@gmail.com>:
> 
> No it's not actually, nevermind.

Yeah, I was going back and forth like that myself. Therefore my question. ;)

I am seeing in an uncomitted change a rare occasion where eor_bucket_destroy() seems to destroy a pool twice. If that is related to a bucket copy, I have not found out yet. But it's one more peculiarity to keep in mind...

Thanks, guys!


> On Thu, May 9, 2019 at 11:24 AM Yann Ylavic <yl...@gmail.com> wrote:
>> 
>> Hmm, if r->pool gets destroyed by the first eor, the
>> eor_bucket_cleanup() for the copy should NULLify its b->data at the
>> same time, so it should be safe no?
>> 
>> On Thu, May 9, 2019 at 11:22 AM Plüm, Rüdiger, Vodafone Group
>> <ru...@vodafone.com> wrote:
>>> 
>>> I think your understanding is correct.
>>> 
>>> Regards
>>> 
>>> Rüdiger
>>> 
>>> 
>>> C2 General
>>> 
>>>> -----Ursprüngliche Nachricht-----
>>>> Von: Stefan Eissing <st...@greenbytes.de>
>>>> Gesendet: Donnerstag, 9. Mai 2019 11:02
>>>> An: dev@httpd.apache.org
>>>> Betreff: eor bucket
>>>> 
>>>> Could someone help me to check my understanding of the eor bucket
>>>> implementation?
>>>> 
>>>> If an eor bucket is ever copied, there are 2 buckets with their b->data
>>>> pointing to the request_rec. Since this is local to the bucket,
>>>> destroying these 2 will call apr_pool_destroy() twice on the pool.
>>>> Correct?
>>>> 
>>>> -Stefan

AW: eor bucket

Posted by Plüm, Rüdiger, Vodafone Group <ru...@vodafone.com>.



C2 General

> -----Ursprüngliche Nachricht-----
> Von: Yann Ylavic <yl...@gmail.com>
> Gesendet: Donnerstag, 9. Mai 2019 11:54
> An: httpd-dev <de...@httpd.apache.org>
> Betreff: Re: eor bucket
> 
> On Thu, May 9, 2019 at 11:37 AM Stefan Eissing
> <st...@greenbytes.de> wrote:
> >
> > > Am 09.05.2019 um 11:32 schrieb Yann Ylavic <yl...@gmail.com>:
> > >
> > > The issue is more that the hooks in eor_bucket_cleanup() will be run
> > > multiple times, rather than a lifetime issue.
> >
> > I read it like this:
> > The cleanup is only registered on the first creation. The copy never
> registers. But the bucket_destroy calls the pool destroy each time.
> 
> Ah yes, apr_bucket_copy() (i.e. apr_bucket_simple_copy()) won't do the
> right thing for eor, there should be an eor_bucket_copy() to register
> the cleanup for the copy too.
> 
> We should also possibly split the eor cleanup in two, one (registered
> first) to run the hooks, and the second for NULLing b->data.
> Both (but mainly the first one) would do nothing is b->data is already
> NULL. That way I think the eor can be safely copied.

I think we should follow a similar design pattern as we do with MMAP/file buckets which use a refcount.

Regards

Rüdiger