Proposal: Close sessions with regards to multiple callers

[Stef Walter <stefw@redhat.com>]

This proposal adds clarifications to C_CloseSession and
C_CloseAllSessions noting their raciness with regard to login state, if
multiple callers of a PKCS#11 token are present within a process.

In addition it adds warnings about when it is appropriate to use
C_CloseAllSessions.

Cheers,

Stef


11.6  Session management functions

*** Remove last clause of paragraph
  5. Call C_CloseSession once for each session that the application
| has with the token.


o C_CloseSession

*** Add paragraph
| Applications should be aware that another caller of the token within |
the same process (such as within a shared library) may have a
| session open with the token, or may open one during or after the
| call to C_CloseSession.

*** Add paragraph
| Unless the application can guarantee that it is aware of all
| sessions, it cannot make assumptions about the login state of the
| token after a C_CloseSession call.


o C_CloseAllSessions

*** Add paragraph
| Applications should be aware that another caller of the token within
| the same process (such as within a shared library) may have a
| session open with the token, or may open one during or after the
| call to C_CloseAllSessions.

*** Add paragraph
| Unless the application can guarantee that it is aware of all
| sessions, it cannot make assumptions about the login state
| of the token after a C_CloseAllSessions call.

*** Add paragraph
| Because other callers within the same process may be using other
| sessions unbeknownst to the caller, this function should only be
| called in response to a user action or other significant event.