SYS_NICE is a capability that allows a process to set thread affinity
and priority, among other things (see capabilities(7) for more info).

In this commit, add a function that allows to determine if the process
has this capability, and try to change the thread affinity and priority,
if requested. If the capability does not exist, the function will simply
not attempt to change the corresponding thread attributes.

To determine if the process has SYS_NICE, libcap can be used. However,
it might not be installed by default. To avoid requiring another
dependency, if we detect that libcap is not present, use a workaround by
try to set a real-time scheduling policy; if it's present, or can be
changed, we assume that the process has SYS_NICE (and clean up, if
relevant).

Simplify reading of capabilities

set_latency_target() attempts to set keep "low latency" by
- writing a specific latency to /dev/cpu_dma_latency
- setting manually the minimum CPU processor frequency to be the maximum

There is no functionality to undo this after stopping the softmodem(s),
and most users are probably not even aware that OAI does this. It is
generally preferable to set this beforehand using a governor or by
disabling sleep states (as outlined in the tutorial, and in a follow-up
commit in the performance tuning docs).

The previous mlockall() call, to lock memory to RAM, is retained in a
new function. There were additional mlockall() calls, which have been
replaced with lock_memory_to_ram(), where necessary.

It's completely unclear what this is supposed to do.

A detached thread cannot be joined with pthread_join(). However, this
is crucial for correct resetting of the nr-softmodem. Therefore, do not
create threads in detached state.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

This work is based on feedback from Thomas Schlichter.
His comments and suggestions were made just after the original MR was merged.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

It looks like :
  - when running on a Fedora-host
  - with generic kernel
  - in a container
  - even in privileged mode

That is not enough and priority/schedule settings is not allowed.

So at runtime, we check and in case, we don't set up priorities.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Mainly comestics and integer type management

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

For whatever reason most of the files had their permission
changed from 644 to 755, which is not wanted.