[tor-bugs] #13291 [Tor]: Fix spawn test failures due to race condition with process exiting early

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#13291: Fix spawn test failures due to race condition with process exiting early
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 Reporter:  teor    |          Owner:
     Type:  defect  |         Status:  new
 Priority:  normal  |      Milestone:
Component:  Tor     |        Version:  Tor: unspecified
 Keywords:          |  Actual Points:
Parent ID:          |         Points:
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 When a spawned process forks, fails, then exits very quickly, (this
 typically occurs when exec fails), there is a race condition between the
 SIGCHLD handler updating the process_handle's fields, and checking the
 process status in those fields. The update can occur before or after the
 tests check the process status.

 This causes intermittent failures in the test spawn_background_fail(),
 typically when the machine is under load. I've created a patch that checks
 whether the process is running or not running (rather than just checking
 if it is running) to avoid this issue.

 I'll submit a github branch once I have the bug number for the changes
 file name.

 tor version: 2.6.0-alpha-dev

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13291>
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