On 11/02/2010 02:33 PM, Chris wrote:
So far no problem, but if I use recursive_mutex instead...
Scenario 2: (NOT OK)
int main() { boost::recursive_mutex io_mutex; io_mutex.lock();
// thread will NOT be blocked ??? boost::recursive_mutex::scoped_lock lock(io_mutex); cout<< "Test" // this statement is executed ??? }
no blocking occurs??
Yep, that's what the 'recursive' means: the same thread is allowed to re-acquire the lock multiple times. After all, if this thread already has acquired a lock on the mutex it's basically a no-op. The resource is protected from concurrent access. If a thread blocks on a non-recursive mutex that it's already locked, wouldn't it be a guaranteed deadlock? Some code might have its reasons, but why would you want a thread to block in the usual case? Just depends on what kind of mutexes you're more familiar with I guess.
How does one lock a recursive_mutex then?
If you want to observe something blocking, create another thread. - Marsh