Does session state have a locking mechanism that serialize the access to state?

Session state implements a reader/writer locking mechanism:

• A page (or frame) that has session state write access (e.g. <%@ Page EnableSessionState=’True’ %>) will hold a writer lock on the session until the request finishes.
• A page (or frame) that has session state read access (e.g. <%@ Page EnableSessionState=’ReadOnly’ %>) will hold a reader lock on the session until the request finishes.
• Reader lock will block a writer lock; Reader lock will NOT block reader lock; Writer lock will block all reader and writer lock.
• That’s why if two frames both have session state write access, one frame has to wait for the other to finish first