I'm writing an application that runs on both Win32 (vs 2005) and Linux (gcc). I was curious what the performance penalty is for a scenario like this: Foo1() { recursive_mutex::scoped_lock lock(mutex); // acquire initial mutex lock Foo2(); ... } Foo2() { recursive_mutex::scoped_lock lock(mutex); // increment lock count ... } Relatively speaking, how much time does it cost to 1) Locking the mutex initially and increment the lock count Vs 2) Determine that a mutex is already locked by the thread and just increment the lock count? I'm also curious how much faster mutex is over recursive_mutex for both platforms. If anybody has done performance profiling or just knows in general the different mutex scenario performance costs, I'd greatly appreciate any info. :) Thanks very much, Scott