[sr-dev] Troubleshooting segfault in shared memory

[Henning Westerholt]

.. use a global variable instead of global parameter, obviously

-----Original Message-----
From: sr-dev <sr-dev-bounces at lists.kamailio.org> On Behalf Of Henning Westerholt
Sent: Thursday, August 26, 2021 10:14 AM
To: Kamailio (SER) - Development Mailing List <sr-dev at lists.kamailio.org>
Subject: Re: [sr-dev] Troubleshooting segfault in shared memory

Hello,

usually, the patter for using shared memory is this:

- allocate the shared memory in main (mod_init) process, use a global parameter
- use the shared memory in child processes, protected by a kamailio lock against concurrent access if you write to it as well

Allocating shared memory in a child process and then accessing it from another child process will not work out of the box.

Have a look to other modules with shared memory, e.g., carrierroute/cr_data.c or similar for an idea.

Cheers,

Henning

--
Henning Westerholt - https://skalatan.de/blog/ Kamailio services - https://gilawa.com 

-----Original Message-----
From: sr-dev <sr-dev-bounces at lists.kamailio.org> On Behalf Of Anthony Alba
Sent: Thursday, August 26, 2021 4:55 AM
To: sr-dev at lists.kamailio.org
Subject: [sr-dev] Troubleshooting segfault in shared memory

Hi sr-dev,

I have a pointer from one child process A that is available to another child process B (this is a custom module I am developing). The object should have been allocated in shared memory by A using ser_malloc and friends and thus accessible from B.

However B is encountering a segfault when accessing this object.

Given a pointer how can I tell whether the memory it is pointing to is valid in all children, i.e, the target is in kamailio shared memory?

Thanks
Anthony Alba

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