4 Nov
2014
4 Nov
'14
6:48 p.m.
On 04/11/14 14:19, Alex Hermann wrote:
On Tuesday 04 November 2014, Daniel-Constantin Mierla
wrote:
If you discovered a flaw in existing code, then should be fixed
properly. It is what I am trying to do as well by discussing your patch.
This is the benefit of open source, reviewing patches for mutual
benefits, and I do hope other people check my commits as well.
I didn't say you didn't get an issue with it and the existing old code
was perfect, I am just trying to understand the issue and be sure it is
the right fix, with no side effects. I will be more than happy to solve
what you found as problem in the old patch, together we what I found not
clear with the last patch.
You said you don't have a backtrace for it and also you didn't provide
any further details about the situation, but now you refer to it as a
'known segfault'. If you can provide more info about the crash, it can
help to really solve the problem.
Just reverting and going back in another buggy state it is not good. I
expressed my opinions that with the patch, it seems we can get back to
the state with dialogs stuck in memory for ever. The config was more
like a temporary solution if you had any pressure on having the patch,
to give everyone an easy option to decide how to use it.
Otherwise, yes, I do want to get it properly fixed, with no options.
Cheers,
Daniel
--
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio Advanced Training, Nov 24-27, Berlin - http://www.asipto.com
On 03/11/14 17:05, Alex Hermann wrote:
I think it is necessary to know it to be able to securely cleanup
dialogs.
On Monday 03 November 2014, Daniel-Constantin
Mierla wrote:
True. But even then refcounting shouldn't be bypassed. For each (cleanup)
situation the expected refcount should be compared to the actual refcount
before deleting.
Not sure what would be expected reference counter value in each
of the
states. In theory, the dialog cannot last for ever in
initial state, so cleaning
it up make sense to stay safe of memory leaks at runtime -- we can print
log messages to alert, but keeping it for ever brings more troubles
(e.g., besides memory leaks, the call limit can be affected).
I agree those must
be cleaned, even though it is not technically a memory
leak, as the dialog pointer is still used in the dialog hash.
As I said, for operations that are long term, I
consider better to keep
dlg index and label (two integers) than increasing the reference count
and storing the pointer (on 64b it is the same size). Then lookup again
the dialog when needed.
Who is talking about "long term" operations? The
duration is not of any
relevance here.
Almost none of the dialog related operations apart from getting the dlg
pointer are protected by locks but by the refcounter. Suppose process 1
obtains a dlg pointer (from the h_entry, and h_id), and upped the refcounter
as a result. It can get scheduled away at any random time, even directly after
obtaining the dlg pointer. If the timer process get scheduled at that moment
and frees the memory of the dlg (disregarding the fact that is is still in
use), how is process 1 to know that?
Finding the reason of what determined you to do
this is important, not to push kind of workaround that we don't fully
understand its purpose and benefits.
IMO, it is not right to keep a dialog in proxy as long as caller/callee
don't have it anymore.
I agree, just not with the method you used to get rid
of the dialog.
You can eventually make the behavior of the patch
configurable, so you
can enable it via modparam, in the current form I don't find it ok.
I'm
not going to make a known segfault path configurable, so i'll revert it if
you insist. But may i kindly suggest you revert your code too which introduced
this code in the first place as, IMHO, it is fundamentally wrong by deleting
an object without checking if it is in use.