CODEWITHSUNDEEP
c++multithreading
razeh
razeh

Reputation: 2765

Can the implementation of std::atomic with respect to locks change a program's behavior from correct to incorrect?

Are there C++ programs that are correct and deadlock free when atomic::is_lock_free returns true, but are undefined or could contain a deadlock when atomic::is_lock_free returns false?

Given that any lock inside an atomic will be acquired and released under the library's control, I can't imagine how to muck things up, but with multithreading and locks there is usually a way :-)

Upvotes: 12

Views: 1421

Answers (1)

axe
axe

Reputation: 2371

In order to have deadlock in a program you need to hold more then one lock simultaneously. Accessing or modifying std::atomic<T> variable may acquire lock according to the C++11 standard, but it releases the lock as soon as function call finished and it doesn't call any user defined function while holding a lock, so you can't have a situation where two (or more) mutexes are locked simultaneously; hence no deadlock is possible with std::atomic internal lockable objects.

Upvotes: 5

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