libflux: disallow message send; prevent segfaults during flux_handle_destroy() #2713
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Problem: Objects registered with a flux_t aux hash that attempt to send an RPC during their destructors will segfault due to a potential to enter flux_handle_destroy() recursively. This happens because adding the handle to future re-increments the usecount to 1. When the usecount drops to 0 again after the future is destroyed, then there is nothing preventing flux_future_destroy() from being called again. Add a destroy_in_progress flag to flux_t, and set this as a sentinel to avoid entering flux_future_destroy() more than once for any given handle. Fixes flux-framework#2711
Problem: The flux handle aux_item hash opens an opportunity for code to attempt to send messages during item destructors, which could cause difficult to diagnose problems or segfaults, and thus should be prevented. Disallow message passing (sending messages at least) during flux handle destruction, and thus all aux hash destructors, by failing flux_send() if the handles "destroy_in_progress" flag is set.
Test that an rpc during aux item destructor fails reliably, and that there is no resulting segfault as described in issue flux-framework#2711.
Codecov Report
@@ Coverage Diff @@
## master #2713 +/- ##
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- Coverage 81.38% 81.38% -0.01%
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Files 248 248
Lines 38789 38791 +2
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Hits 31570 31570
- Misses 7219 7221 +2
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alrighty-then, setting merge-when-passing. |
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This PR is split off #2710. It fixes two issues discussed there:
flux_handle_destroy()by adding adestroy_in_progressflag to flux handles.Also adds a trivial testcase that segfaulted before these fixes.