- Clean up the namespace of this module and enable the encode/decode
functions and printing functions.
- Move the code that actually generates the UUID out of the system call
routine and into its own function.
> Call dom_dispose() for any SCM_RIGHTS message that went through the
> read path rather than recv. Previously, if an fd was passed via
> sendmsg() but was consumed by the receiver via read() the ref count
> was incremented and never decremented and so the ref count would
> never reach zero even when there was no long any processes holding
> the file open (this was especially bad for locked fds).
loadable drivers and user controlled attach/detach of devices.
An outline was given in
http://mail-index.NetBSD.org/tech-kern/2004/08/11/0000.html
To cite the relevant parts:
-Add a "child detached" and a "rescan" method (both optional)
to the device driver. (This is added to the "cfattach" for now
because this is under the driver writer's control. Logically
it belongs more to the "cfdriver", but this is automatically
generated now.)
The "child detached" is called by the autoconf framework
during config_detach(), after the child's ca_detach()
function was called but before the device data structure
is freed.
The "rescan" is called explicitely, either after a driver LKM
was loaded, or on user request (see the "control device" below).
-Add a field to the device instance where the "locators" (in
terms of the autoconf framework), which describe the actual
location of the device relatively to the parent bus, can be
stored. This can be used by the "child detached" function
for easier bookkeeping (no need to lookup by device instance
pointer). (An idea for the future is to use this for generation
of optimized kernel config files - like DEC's "doconfig".)
-Pass the locators tuple describing a device's location to
various autoconf functions to support the previous. And since
locators do only make sense in relation to an "interface
attribute", pass this as well.
-Add helper functions to add/remove supplemental "cfdata"
arrays. Needed for driver LKMs.
There is some code duplication which will hopefully resolved
when all "submatch"-style functions are changed to accept the
locator argument.
Some more cleanup can take place when config(8) issues more
information about locators, in particular the length and default
values. To be done later.
* Rather than using mnt_maxsymlinklen to indicate that a file systems returns
d_type fields(!), add a new internal flag, IMNT_DTYPE.
Add 3 new elements to ufsmount:
* um_maxsymlinklen, replaces mnt_maxsymlinklen (which never should have existed
in the first place).
* um_dirblksiz, which tracks the current directory block size, eliminating the
FS-specific checks littered throughout the code. This may be used later to
make the block size variable.
* um_maxfilesize, which is the maximum file size, possibly adjusted lower due
to implementation issues.
Sync some bug fixes from FFS into ext2fs, particularly:
* ffs_lookup.c 1.21, 1.28, 1.33, 1.48
* ffs_inode.c 1.43, 1.44, 1.45, 1.66, 1.67
* ffs_vnops.c 1.84, 1.85, 1.86
Clean up some crappy pointer frobnication.
* Process A is closing one file descriptor belonging to a device. In doing so,
ffs_update() is called and starts writing a block synchronously. (Note: This
leaves the vnode locked. It also has other instances -- stdin, et al -- of
the same device open, so v_usecount is definitely non-zero.)
* Process B does a revoke() on the device. The revoke() has to wait for the
vnode to be unlocked because ffs_update() is still in progress.
* Process C tries to open() the device. It wedges in checkalias() repeatedly
calling vget() because it returns EBUSY immediately.
To fix, this:
* checkalias() now uses LK_SLEEPFAIL rather than LK_NOWAIT. Therefore it will
wait for the vnode to become unlocked, but it will recheck that it is on the
hash list, in case it was in the process of being revoke()d or was revoke()d
again before we were woken up.
* Since we're relying on the vnode lock to tell us that the vnode hasn't been
removed from the hash list *anyway*, I have moved the code to remove it into
the DOCLOSE section of vclean(), inside the vnode lock.
In the example at hand, process A was sh(1), process B was a child of init(8),
and process C was syslogd(8).
from Stephan Uphoff, FreeBSD PR/69964.
(http://www.freebsd.org/cgi/query-pr.cgi?pr=69964)
> The LK_WANT_EXCL and LK_WANT_UPGRADE bits act as mini-locks and can block
> other threads.
> Normally this is not a problem since the mini locks are upgraded to full loc
> and the release of the locks will unblock the other threads.
> However if a thread reset the bits without optaining a full lock
> other threads are not awoken.
> This can happens if obtaining the full lock fails because of a LK_SLEEPFAIL,
> or a signal (if lock priority includes PCATCH .. don't think this is used).
ensure that no one else have the same lock.
a patch from Stephan Uphoff, FreeBSD PR/69934.
(http://www.freebsd.org/cgi/query-pr.cgi?pr=69934)
> Upgrading a lock does not play well together with acquiring
> an exclusive lock and can lead to two threads being
> granted exclusive access.
>
> Problematic sequence:
> Thread A acquires a previous unlocked lock in shared mode.
> Thread B tries to acquire the same lock in exclusive mode
> and blocks.
> Thread A upgrades its lock - waking up thread B.
> Thread B wakes up and also acquires the same lock as it only checks
> if the lock is not shared or if someone wants to upgrade the lock
> and not if someone already upgraded the lock to an exclusive lock.
long, not an int, and this causes "problems" on LP64be machines
(sparc64, etc). Assign the value to a temporary int and instrument
that instead. Should be fine until someone wants a message buffer
larger than two gigabytes.
enami