133882 - Subsystem shutdown registration mechanism for NSS

Status: RESOLVED DUPLICATE of bug 326482

(NSS :: Libraries, enhancement, P2)

Description

[Julien Pierre]

It would be very useful to have a mechanism through which application 
or NSS subsystems that depend on the NSS core could register a shutdown callback 
function . This function would be called upon entry of NSS_Shutdown().
There could be several functions registered in a LIFO queue.

An example of internal subsystem that could immediately benefit from this would 
be SSL to automatically cleanup the session cache upon NSS_Shutdown().

Another immediate use for this shutdown callback mechanism would be client and 
server plug-ins that want to access NSS directly and may start background 
threads making NSS calls for their own purpose. This would pose a problem if 
these client and server applications, unaware of the plug-in's use of NSS, 
called NSS_Shutdown(), without calling the plug-in's shutdown function, for 
example in case the browser wants to keep plug-ins loaded when switching 
profiles. A crash would follow in that situation. But the shutdown registration 
would take care of the problem very nicely.

Comment 1

[Nelson Bolyard (seldom reads bugmail)]

This is an interesting idea.  On some Unix systems, the SSL library starts
a thread to look for locks held by dead processes.  It might be nice if 
NSS_Shutdown stopped that thread and closed the server session cache memory
map as a side effect.  It might be nice if NSS_Shutdown cleared the client 
session cache as a side effect.  We wouldn't want NSS_Shutdown to call SSL
functions by name to do this because then libNSS would depend on libSSL.
But if NSS_Shutdown had a callback mechanism, that could be used for these
purposes.  

I'd guess that the callback mechanism might need a flag to indicate whether
the callback function should be called before, or after, the PKCS#11 tokens
were shutdown.

Comment 2

[Wan-Teh Chang]

Changed the QA contact to Bishakha.

Comment 3

[Julien Pierre]

This was fixed by Bob as part of bug 326482. Marking as dupe.