When to use recursive mutex?

c++ multithreading recursion mutex recursive-mutex
jasonline picture jasonline · Mar 10, 2010 · Viewed 52.3k times · Source

I understand recursive mutex allows mutex to be locked more than once without getting to a deadlock and should be unlocked the same number of times. But in what specific situations do you need to use a recursive mutex? I'm looking for design/code-level situations.

Answer

Antti Huima picture Antti Huima · Mar 10, 2010

For example when you have function that calls it recursively, and you want to get synchronized access to it:

void foo() {
   ... mutex_acquire();
   ... foo();
   ... mutex_release();
}

without a recursive mutex you would have to create an "entry point" function first, and this becomes cumbersome when you have a set of functions that are mutually recursive. Without recursive mutex:

void foo_entry() {
   mutex_acquire(); foo(); mutex_release(); }

void foo() { ... foo(); ... }

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