Now that we have these new functions,
we can also make them return an error
instead of calling sysfatal() like
postmountsrv().
Remove the confusing Srv.srvfd, as it
is only temporarily used and return
it from postsrv() instead.
To use srvrease()/srvaquire() we need to have a way to spawn
new processes to handle the service loop. This functionality
was provided by the internal _forker() function which was
eigther rfork or libthread based implementation depending on
if postmountsrv() or threadpostmountsrv() where called.
For servers who want to use srv() directly, _forker would not
be initialized so srvrelease() could not be used.
To untangle this, we get rid of the global _forker handler
and put the handler in the Srv structure. Which will get
initialized (when nil) to eigther srvforker() or threadsrvforker()
depending on if the thread or non-thread entry points where used.
For symmetry, we provde new threadsrv() and threadpostsrv()
functions which handle the default initialization of Srv.forker.
This also allows a user to provide his own forker function,
maybe to conserve stack space.
To avoid dead code, we put each of these function in their
own object file. Note, this also allows a user to define its
own srvforker() symbol.
with the latest changes to shr(3), we can use ORCLOSE on
the control file to get the mount in the share automatically
removed when the server exits or something goes wrong during
postsharesrv().
do not expose postfd() and sharefd() functions. they where
undocumented and leak the control file descriptors.
it is unclear how Srv.nopipe flag should work inside
postmountserv(). if a server wants to serve on stdio
descriptors, he can just call srv() after initializing
Srv.infd and Srv.outfd.
The Srv.leavefdsopen hack can be removed now that acme
win has been fixed.
the process is *NOT* allowed to exit after a srvrelease() as
it still holds a reference (srv->rref) preventing the srv
from beging freed/ended (listensrv) before srvacquire().
