Function kernel::process_checker::is_runnable

source · 
pub fn is_runnable<AU: AppUniqueness>(
    process: &dyn Process,
    processes: &[Option<&dyn Process>],
    id_differ: &AU
) -> bool
Expand description

Return whether process can run given the identifiers, version numbers, and execution state of other processes. A process is runnable if its credentials have been approved, it is in the Terminated state, and one of the following conditions hold:

  1. Its Application Identifier and Short ID are different from all other processes, or
  2. For every other process that shares an Application Identifier or Short ID: 2A. If it has a lower or equal version number, it is not running 2B. If it has a higher version number, it is in the Terminated, CredentialsUnchecked, or CredentialsFailed state.

Case 2A is because if a lower version number is currently running, it must be stopped before the higher version number can run. Case 2B is so that a lower or equal version number can be run if the higher or equal has been explicitly stopped (Terminated) or cannot run (Unchecked/Failed). This second case is designed so that at boot the highest version number will run (it will be in the CredentialsApproved state when this test runs at boot), but it can be stopped to let a lower version number run.