CODEWITHSUNDEEP
c++multithreadingboostlocking
J0hnD0e
J0hnD0e

Reputation: 87

c++ lock across methods

I have a data-structure that is not thread-safe. Multiple threads are reading and writing to that data-structure in 2 methods. (the order of calls is rather random) My approach to this problem was using a unique_lock like shown below:

struct test {

  void func1() {
    boost::unique_lock<boost::mutex> lock(_mutex);
    // modify data-structure
  }


  void func2() {
    boost::unique_lock<boost::mutex> lock(_mutex);  
    // modify data-structure
  }

   boost::mutex _mutex;
}

I though, that with this code, only one thread at a time is allowed to access the data, as the mutex is shared across the two methods.
But somehow may program triggers a bug in the data-structure, which I am unable to reproduce in my single-threaded test-cases...

Do I have to use the boost::unique_lock in both methods and then call

lock()
unlock()

on it?

Upvotes: 1

Views: 237

Answers (1)

J0hnD0e
J0hnD0e

Reputation: 87

the locking mechanism, as described, was not the reason for the bug.
Well, actually it was ;)
Outside of the critical section i called 

datastructure.empty()

because in an earlier version this method was threadsave.

Thanks to "Kerrek SB" for pointing on thread-sanitizer, as it's output guided me to the bug.

Upvotes: 0

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