Previously each request was executed on its own callcontext and
switched to every time the request was being processed. Now requests
borrow the mainloop context and switch only if/when they yield.
This takes two context switches away from a file system request
bringing down the typical amounts 2->0 (e.g. dtfs) and 4->2 (e.g.
psshfs).
The interfaces for manually executing requests changed a bit:
puffs_dispatch_create() and puffs_dispatch_exec() must now be used.
They are not tested, as nothing in-tree wants them and I doubt
anyone else is really interested in them either.
Also do some misc code cleanup related to execution contexts. The
"work-in-progress checkpoint" committed over a year ago was starting
to look slightly weed-infested.
Get rid of the original puffs_req(3) framework and use puffs_framebuf(3)
instead for file system requests. It has the advantage of being
suitable for transporting a distributed message passing protocol
and therefore us being able to run the file system server on any
host.
Ok, puffs is not quite here yet: libpuffs needs to grow request
routing support and the message contents need to be munged into a
host independent format. Saying which format would be telling,
but it might begin with an X, end in an L and have the 13th character
in the middle. Keep an eye out for the sequels: Parts 3+m/n.
also synchronizes with puffs_mount() and does not return (exit) in the
parent process until the file system has been mounted. This makes
it possible to reliably run e.g. mount_foo jippi /kai ; cd /kai/ee
servers. Calling daemon() (i.e. fork()ing) inside a library can
cause nice surprises for e.g. threaded programs. As discussed with
Greg Oster & others.
support removal and addition of i/o file descriptors on the fly.
* detect closed file descriptors
* automatically free waiters of a dead file descriptor
* give the file server the possibility to specify a callback which
notifies of a dead file descriptor
* move loop function to be a property of the mainloop instead of
framebuf (doesn't change effective behaviour)
* add the possibility to configure a timespec parameter which
attempts to call the loop function periodically
* move the event loop functions from the puffs_framebuf namespace
to puffs_framev to differential between pure memory management
functions
