[PATCH 0/3] posix timers: Extend kernel API to report more info about timers

[Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

Hi.

I'm working on the checkpoint-restore project (http://criu.org), briefly
it's aim is to collect information about process' state and saving it so
that later it is possible to recreate the processes in the very same state
as they were, using the collected information.

One part of the task's state is the posix timers that this task has created.
Currently kernel doesn't provide any API for getting information about
what timers are currently created by process and in which state they are.
I'd like to extend the posix timers API to provide more information about
timers.

Another problem with timers is the timer ID. Currently IDs are generated
from global IDR and this makes it impossible to restore a timer from
the saved state in general, as the required ID may be already busy at the
time of restore.

That said, I propose to

1. Change the way timer IDs are generated. This was done some time ago, so
   I'm just re-sending this patch;
2. Add a system call that will list timer IDs created by the calling process;
3. Add a system call that will allow to get the sigevent information about
   particular timer in the sigaction-like manner.

This is actually an RFC to start discussion about how the described problems
can be addressed. Thus, if the approach with new system calls is not acceptable,
I'm OK to implement this in any other form.

Thanks,
Pavel