param save: Add a blocking API for param saves to be used from shell.

[ThomasDebrunner]

Solved Problem

After the latest param rework, the file lock in param_save_default was changed to a trylock, to prevent any blocking in the param system. This makes param_save_default occasionally fail, if it is called from multiple threads at the same time. This is correct, but unexpected especially when used from the shell.

Solution

This changes the param_save_default function to have be either blocking or non-blocking.

From the shell and from modules that expect a synchronous API, the blocking version is called. From the work queue, the non blocking version is called.

This also modifies the autosave worker, to re-schedule writing up to three times, in case writes fail.

Changelog Entry

For release notes:

• Bugfix: Blocking API for param save

Alternatives

As an alternative, we could disable the autosave worker in the CI tests. This would solve the error in the CI tests. But still, a user typing in param save could still hit it then.

Test coverage

• All unit tests still pass
• Bench test on v5x

[mrpollo]

Hey @ThomasDebrunner thanks for the PR. Would you mind fixing the style check test?

[ThomasDebrunner]

Fixed style

[bkueng]

CI failure is unrelated, something with the Micro-XRCE-DDS-Client update.

 FAILED: src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-stamp/libmicroxrceddsclient_project-configure 
cd /__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-build && /usr/bin/cmake -P /__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-stamp/libmicroxrceddsclient_project-configure-RelWithDebInfo.cmake && /usr/bin/cmake -E touch /__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-stamp/libmicroxrceddsclient_project-configure
CMake Error at /__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-stamp/libmicroxrceddsclient_project-configure-RelWithDebInfo.cmake:16 (message):
  Command failed: 1

   '/usr/bin/cmake' '-C/__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/tmp/libmicroxrceddsclient_project-cache-RelWithDebInfo.cmake' '-GNinja' '/__w/PX4-Autopilot/PX4-Autopilot/src/modules/uxrce_dds_client/Micro-XRCE-DDS-Client'

  See also

    /__w/PX4-Autopilot/PX4-Autopilot/build/emlid_navio2_default/src/modules/uxrce_dds_client/src/libmicroxrceddsclient_project-stamp/libmicroxrceddsclient_project-configure-*.log

EDIT: the cmake version in the container px4io/px4-dev-armhf is too old:

CMake Error at CMakeLists.txt:18 (cmake_minimum_required):
  CMake 3.16 or higher is required.  You are running version 3.13.4