What is the minimum number of threads required to cause a deadlock?

The minimum number of threads required for a deadlock to occur is two.

A deadlock occurs when two or more threads hold resources simultaneously and each waits for the resource held by the other. For example:

• Thread A acquires resource 1 and waits for resource 2.
• Thread B acquires resource 2 and waits for resource 1.

Both threads are blocked forever because each is waiting for a resource held by the other.

Pseudo-code example:

// Thread 1
lock(resource1)
wait()
lock(resource2)

// Thread 2
lock(resource2)
wait()
lock(resource1)

Thus, a deadlock requires only two threads and two resources.