[phosphor-software-manager] potential out of order for reboot guard enable and disable procedure

[Heyi Guo]

Hi all,

We found reboot might be permanently disabled after running BMC image 
update with curl command. The journal log showed the steps of reboot 
guard enable and disable were out of order:

Mar 05 20:32:58 ali2600 systemd[1]: Starting Enable a guard that blocks 
BMC reboot...
Mar 05 20:32:58 ali2600 phosphor-image-updater[370]: BMC activation has 
ended - BMC reboots are re-enabled.
Mar 05 20:32:58 ali2600 systemd[1]: Starting Removes the guard that 
blocks BMC reboot...
Mar 05 20:32:58 ali2600 phosphor-image-updater[370]: BMC image ready, 
need reboot to get activated.
Mar 05 20:32:58 ali2600 systemd[1]: reboot-guard-disable.service: Succeeded.
Mar 05 20:32:58 ali2600 systemd[1]: Finished Removes the guard that 
blocks BMC reboot.
Mar 05 20:32:59 ali2600 systemd[1]: reboot-guard-enable.service: Succeeded.
Mar 05 20:32:59 ali2600 systemd[1]: Finished Enable a guard that blocks 
BMC reboot.

It seems systemd would not guarantee the completion order for StartUnit 
operations, while I think this is critical for firmware upgrade 
procedure. Shall we switch to normal C++ implementation to create and 
remove reboot guaud configuration files, to guarantee the order of these 
sequential steps?

Thanks,

Heyi