Acquire a lock on two mutexes and avoid deadlock

Question

The following code contains a potential deadlock, but seems to be necessary: to safely copy data to one container from another, both containers must be locked to prevent cha

Answer 1

How about this?

void foo::copy(const foo & rhs)
{
    scopedLock lock(rhs.pMutex); // release mutex in destructor
    foo tmp(rhs);
    swap(tmp); // no throw swap locked internally
}

This is exception safe, and pretty thread safe as well. To be 100% thread save you'll need to review all code path and than re-review again with another set of eyes, after that review it again...