Coverity report Oct 31st, 2024

We got a report of three CID from a patch we merged recently in 048+

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*** CID 1634143:  Concurrent data access violations  (MISSING_LOCK)
/src/lib/evloop/workqueue.c: 609 in threadpool_free_()
603           workerthread_free(pool->threads[i]);
604
605         tor_free(pool->threads);
606       }
607
608       if (pool->update_args)
>>>     CID 1634143:  Concurrent data access violations  (MISSING_LOCK)
>>>     Accessing "pool->free_update_arg_fn" without holding lock "tor_mutex_t.mutex". Elsewhere, "threadpool_t.free_update_arg_fn" is written to with "tor_mutex_t.mutex" held 1 out of 1 times.
609         pool->free_update_arg_fn(pool->update_args);
610
611       if (pool->reply_event) {
612         tor_event_del(pool->reply_event);
613         tor_event_free(pool->reply_event);
614       }

** CID 1634142:  Error handling issues  (CHECKED_RETURN)
/src/lib/evloop/workqueue.c: 612 in threadpool_free_()

Then:

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*** CID 1634142:  Error handling issues  (CHECKED_RETURN)
/src/lib/evloop/workqueue.c: 612 in threadpool_free_()
606       }
607
608       if (pool->update_args)
609         pool->free_update_arg_fn(pool->update_args);
610
611       if (pool->reply_event) {
>>>     CID 1634142:  Error handling issues  (CHECKED_RETURN)
>>>     Calling "event_del" without checking return value (as is done elsewhere 4 out of 5 times).
612         tor_event_del(pool->reply_event);
613         tor_event_free(pool->reply_event);
614       }
615
616       if (pool->reply_queue)
617         replyqueue_free(pool->reply_queue);

Finally:

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*** CID 1634141:  Concurrent data access violations  (MISSING_LOCK)
/src/lib/evloop/workqueue.c: 608 in threadpool_free_()
602         for (int i = 0; i != pool->n_threads; ++i)
603           workerthread_free(pool->threads[i]);
604
605         tor_free(pool->threads);
606       }
607
>>>     CID 1634141:  Concurrent data access violations  (MISSING_LOCK)
>>>     Accessing "pool->update_args" without holding lock "tor_mutex_t.mutex". Elsewhere, "threadpool_t.update_args" is written to with "tor_mutex_t.mutex" held 1 out of 1 times.
608       if (pool->update_args)
609         pool->free_update_arg_fn(pool->update_args);
610
611       if (pool->reply_event) {
612         tor_event_del(pool->reply_event);
613         tor_event_free(pool->reply_event);