The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Wednesday, June 17, 2015

It's never lupus nor a compiler bug

While testing “Project: Sippy-Cup,” one of the components I was using for testing asserted:

tpp.c:63: __pthread_tpp_change_priority: Assertion `new_prio == -1 || (new_prio >= __sched_fifo_min_prio && new_prio <= __sched_fifo_max_prio)' failed.

This is not good. This wasn't our code that called assert(), but pthreads.

Sigh.

The hardest part of debugging this was getting it to happen consistently (yes, it's one of those bugs) to test out various hypotheses.

It wasn't neglecting to initialize a variable. It wasn't a compiler bug. It turned out to be a abuse of the mutex API, where one thread locks a mutex, and some other thread attempts to unlock the mutex.

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