/v1/actions: run only one action per object at the same time

[Al2Klimov]

so that actions on the same object don't disturb or even deadlock each other.

fixes #9916 closes #9924

@ymartin-ovh What about this idea of mine? And if yes, does it actually fix your problem?

[julianbrost]

so that actions on the same object [...] deadlock each other

I doubt that would work out: Within Checkable::ProcessCheckResult(), there are three places where the ObjectLock on the checkable is released. As the ObjectLock is a recursive mutex, if you call that while holding one on the same object externally, these unlock operations effectively do nothing anymore. So this PR might actually even introduce new deadlocks.

[Al2Klimov]

Would you prefer a separate mutex?

[ymartin-ovh]

@Al2Klimov I don't know if it will fix my issue. But, when your PR is ready, I can build Icinga2 with your diff to check.

[ymartin-ovh]

Hello

I tested your proposal and I still experience deadlock on Icinga2 API with this. Have the issue twice last friday and today.

I still have two concurrent addcomment operations

all-threads-backtraces.txt lock-traces.txt

Regards