Concept :
I'm running a daemon process providing a shared memory interface towards
its "clients".
(This is all running on the same box)
Unrelated (no child processes) clients attach to this Daemon using a
"well known key".
Once this Daemon is alive and kicking it creates a shared memory struct.
In this struct the PID of this daemon is present.
This type of IPC is chosen (instead of sockets) for the massive data
structs I need to shared with clients. It's also much faster.
For my application it is quite important that clients attached to this
interface are aware of the status of the daemon.
Keep in mind that the shared memory block remains present when the
daemon dies for some reason.
When the daemon gets killed voluntarily the shared mem is marked for
deletion but not removed untill the last client detaches.
When the daemon gets killed unvoluntarily the shared mem is not even
marked for deletion.
Questions:
How can clients check the status of the daemon??
Using kill (DEAMON_PID,0) is not a real solution, since clients could be
run as user NOBODY and therefor have no privileges to do this.
Let me know if anyone sees a good technique for checking the status of
an unrelated process.
I have a feeling that semaphores could bring something, please comment.
Besides the fact that semaphores look quite complicated, I couldn't find
any examples that fit in above concept. Any example is welcome.
Regards,
Richard van Ulden
MuLogic
