Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Put the general logic for being a CPU hog into a new function
should_yield(). Use this in various places. Encapsulate the common
case of check-and-yield into a new function maybe_yield().

Change several checks for a magic number of iterations to use
should_yield() instead.

MFC after: 1 week

Request a CPU private mapping from sf_buf_alloc().

Start all license/copyright notice comments with /*-, per tradition

Properly free the temporary sf_buf in uiomove_fromphys() if a copyin or
copyout fails.

Obtained from: DragonFlyBSD

Remove checks for curthread == NULL - it can't happen.

Move TDF_DEADLKTREAT into td_pflags (and rename it accordingly) to avoid
having to acquire sched_lock when manipulating it in lockmgr(), uiomove(),
and uiomove_fromphys().

Reviewed by: jhb

Remove advertising clause from University of California Regent's
license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

In some cases, sf_buf_alloc() should sleep with pri PCATCH; in others, it
should not. Add a new parameter so that the caller can specify which is
the case.

Reported by: dillon

Add an implementation of uiomove_fromphys() for i386. This implementation
uses sf_buf_alloc() and sf_buf_free() to create and destroy the necessary
ephemeral mappings.