option is used (not on by default).
- In the case of trying to lock a mutex, if the MTX_CONTESTED flag is set,
then we can safely read the thread pointer from the mtx_lock member while
holding sched_lock. We then examine the thread to see if it is currently
executing on another CPU. If it is, then we keep looping instead of
blocking.
- In the case of trying to unlock a mutex, it is now possible for a mutex
to have MTX_CONTESTED set in mtx_lock but to not have any threads
actually blocked on it, so we need to handle that case. In that case,
we just release the lock as if MTX_CONTESTED was not set and return.
- We do not adaptively spin on Giant as Giant is held for long times and
it slows SMP systems down to a crawl (it was taking several minutes,
like 5-10 or so for my test alpha and sparc64 SMP boxes to boot up when
they adaptively spinned on Giant).
- We only compile in the code to do this for SMP kernels, it doesn't make
sense for UP kernels.
Tested on: i386, alpha, sparc64
the relevant classes.
Some methods may implement various "magic spaces", this is reserved
or magic areas on the disk, set a side for various and sundry purposes.
A good example is the BSD disklabel and boot code on i386 which occupies
a total of four magic spaces: boot1, the disklabel, the padding behind
the disklabel and boot2. The reason we don't simply tell people to
write the appropriate stuff on the underlying device is that (some of)
the magic spaces might be real-time modifiable. It is for instance
possible to change a disklabel while partitions are open, provided
the open partitions do not get trampled in the process.
Sponsored by: DARPA & NAI Labs.
it, which means that relative paths will be expanded to absolute paths, and
filenames without a path will end up with their absolute path included as
well. This aids tremendously in debugging a build using our make(1) with
multiple Makefile's, such as when there is a syntax error in a file in a
sub-directory as per <bsd.subdir.mk>. Normally we'd end up with just
"Makefile" known about the Makefile in question, which means that an error
would be useless for someone trying to debug their build system, now we
end up with a complete real pathname for the Makefile.
So mostly this is useful in a debugging context, but possibly others too
(I haven't thought of them yet, but they probably are more useful if you
make Dir_FindFile use realpath(3), but that's another story).
Reviewed by: -current
MFC after: 2 weeks
maintained for years and is very old code. If there is any need for
it, I suspect that ports would be a better place.
No objection from: current@freebsd.org
though I would personally prefer to see the broken nameservers fixed
instead of standards compliant applications work around them, I can't
force FreeBSD users to help fight that battle.
Submitted by: Damon Anton Permezel <dap@damon.com>
MFC after: 2 days
pending RE approval
changing indentation and some comments. Main goal is not perfect style,
but just to reduce differences with NetBSD. The object code is exactly
the same after this change as before it (except for assert() statements
which have moved).
Reviewed by: /sbin/md5 on i386
Obtained from: NetBSD
value of the tag or data field.
Add macros for getting the page shift, size and mask for the physical page
that a tte maps (which may be one of several sizes).
Use the new cache functions for invalidating single pages.
