Editing Monitor (synchronization) (section)

===Problem statement===
For many applications, mutual exclusion is not enough. Threads attempting an operation may need to wait until some condition {{var|P}} holds true. A [[busy waiting]] loop

 '''while''' '''not''' ( {{var|P}} ) '''do''' '''skip'''

will not work, as mutual exclusion will prevent any other thread from entering the monitor to make the condition true. Other "solutions" exist such as having a loop that unlocks the monitor, waits a certain amount of time, locks the monitor and checks for the condition {{var|P}}. Theoretically, it works and will not deadlock, but issues arise. It is hard to decide an appropriate amount of waiting time: too small and the thread will hog the CPU, too big and it will be apparently unresponsive. What is needed is a way to signal the thread when the condition {{var|P}} is true (or ''could'' be true).