Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

MFcalloutng:
Introduce sbt variants of msleep(), msleep_spin(), pause(), tsleep() in
the KPI, allowing to specify timeout in 'sbintime_t' rather than ticks.

Sponsored by: Google Summer of Code 2012, iXsystems inc.
Tested by: flo, marius, ian, markj, Fabian Keil

Introduce the same mutex-wise fix in r227758 for sx locks.

The functions that offer file and line specifications are:
- sx_assert_
- sx_downgrade_
- sx_slock_
- sx_slock_sig_
- sx_sunlock_
- sx_try_slock_
- sx_try_xlock_
- sx_try_upgrade_
- sx_unlock_
- sx_xlock_
- sx_xlock_sig_
- sx_xunlock_

Now vm_map locking is fully converted and can avoid to know specifics
about locking procedures.
Reviewed by: kib
MFC after: 1 month

Constify arguments for locking KPIs where possible.

This enables locking consumers to pass their own structures around as const and
be able to assert locks embedded into those structures.

Reviewed by: ed, kib, jhb

- Merge changes to the base system to support OFED. These include
a wider arg2 for sysctl, updates to vlan code, IFT_INFINIBAND,
and other miscellaneous small features.

When releasing a read/shared lock we need to use a write memory barrier
in order to avoid, on architectures which doesn't have strong ordered
writes, CPU instructions reordering.

Diagnosed by: fabio
Reviewed by: jhb
Tested by: Giovanni Trematerra
<giovanni dot trematerra at gmail dot com>

In non-debugging mode make this define (void)0 instead of nothing. This
helps to catch bugs like the below with clang.

if (cond); <--- note the trailing ;
something();

Approved by: ed (mentor)
Discussed on: current@

Reverse the logic for ADAPTIVE_SX option and enable it by default.
Introduce for this operation the reverse NO_ADAPTIVE_SX option.
The flag SX_ADAPTIVESPIN to be passed to sx_init_flags(9) gets suppressed
and the new flag, offering the reversed logic, SX_NOADAPTIVE is added.

Additively implements adaptive spininning for sx held in shared mode.
The spinning limit can be handled through sysctls in order to be tuned
while the code doesn't reach the release, after which time they should
be dropped probabilly.

This change has made been necessary by recent benchmarks where it does
improve concurrency of workloads in presence of high contention
(ie. ZFS).

KPI breakage is documented by __FreeBSD_version bumping, manpage and
UPDATING updates.

Requested by: jeff, kmacy
Reviewed by: jeff
Tested by: pho

Add the OpenSolaris dtrace lockstat provider. The lockstat provider
adds probes for mutexes, reader/writer and shared/exclusive locks to
gather contention statistics and other locking information for
dtrace scripts, the lockstat(1M) command and other potential
consumers.

Reviewed by: attilio jhb jb
Approved by: gnn (mentor)

Fix compilation of arm's AVILA.

Compilation of the AVILA kernel failed because of two reasons:

- It needed curthread, which is defined through <sys/pcpu.h>.

- It still referred the softc's sc_mtx field, which has been replaced by
sc_lock three weeks ago.

To solve the first problem, I decided to include <sys/pcpu.h> in
<sys/sx.h>, which also seems to be done by <sys/mutex.h> and
<sys/rwlock.h>. Those header files also require curthread.

Approved by: jhb

- Re-implement lock profiling in such a way that it no longer breaks
the ABI when enabled. There is no longer an embedded lock_profile_object
in each lock. Instead a list of lock_profile_objects is kept per-thread
for each lock it may own. The cnt_hold statistic is now always 0 to
facilitate this.
- Support shared locking by tracking individual lock instances and
statistics in the per-thread per-instance lock_profile_object.
- Make the lock profiling hash table a per-cpu singly linked list with a
per-cpu static lock_prof allocator. This removes the need for an array
of spinlocks and reduces cache contention between cores.
- Use a seperate hash for spinlocks and other locks so that only a
critical_enter() is required and not a spinlock_enter() to modify the
per-cpu tables.
- Count time spent spinning in the lock statistics.
- Remove the LOCK_PROFILE_SHARED option as it is always supported now.
- Specifically drop and release the scheduler locks in both schedulers
since we track owners now.

In collaboration with: Kip Macy
Sponsored by: Nokia

Fix some problems with lock_profiling in sx locks:
- Adjust lock_profiling stubs semantic in the hard functions in order to be
more accurate and trustable
- Disable shared paths for lock_profiling. Actually, lock_profiling has a
subtle race which makes results caming from shared paths not completely
trustable. A macro stub (LOCK_PROFILING_SHARED) can be actually used for
re-enabling this paths, but is currently intended for developing use only.
- Use homogeneous names for automatic variables in hard functions regarding
lock_profiling
- Style fixes
- Add a CTASSERT for some flags building

Discussed with: kmacy, kris
Approved by: jeff (mentor)
Approved by: re

Add functions sx_xlock_sig() and sx_slock_sig().
These functions are intended to do the same actions of sx_xlock() and
sx_slock() but with the difference to perform an interruptible sleep, so
that sleep can be interrupted by external events.
In order to support these new featueres, some code renstruction is needed,
but external API won't be affected at all.

Note: use "void" cast for "int" returning functions in order to avoid tools
like Coverity prevents to whine.

Requested by: rwatson
Tested by: rwatson
Reviewed by: jhb
Approved by: jeff (mentor)

style(9) fixes for sx locks.

Approved by: jeff (mentor)

Rename the macros for assertion flags passed to sx_assert() from SX_* to
SA_* to match mutexes and rwlocks. The old flags still exist for
backwards compatiblity.

Requested by: attilio

Expose sx_xholder() as a public macro. It returns a pointer to the thread
that holds the current exclusive lock, or NULL if no thread holds an
exclusive lock.

Requested by: pjd

Add a new SX_RECURSE flag to make support for recursive exclusive locks
conditional. By default, sx(9) locks are back to not supporting recursive
exclusive locks.

Submitted by: attilio

Add destroyed cookie values for sx locks and rwlocks as well as extra
KASSERTs so that any lock operations on a destroyed lock will panic or
hang.

Fixes to sx for newsx - fix recursed case and move out of inline

Submitted by: Attilio Rao <attilio@freebsd.org>

Optimize sx locks to use simple atomic operations for the common cases of
obtaining and releasing shared and exclusive locks. The algorithms for
manipulating the lock cookie are very similar to that rwlocks. This patch
also adds support for exclusive locks using the same algorithm as mutexes.

A new sx_init_flags() function has been added so that optional flags can be
specified to alter a given locks behavior. The flags include SX_DUPOK,
SX_NOWITNESS, SX_NOPROFILE, and SX_QUITE which are all identical in nature
to the similar flags for mutexes.

Adaptive spinning on select locks may be enabled by enabling the
ADAPTIVE_SX kernel option. Only locks initialized with the SX_ADAPTIVESPIN
flag via sx_init_flags() will adaptively spin.

The common cases for sx_slock(), sx_sunlock(), sx_xlock(), and sx_xunlock()
are now performed inline in non-debug kernels. As a result, <sys/sx.h> now
requires <sys/lock.h> to be included prior to <sys/sx.h>.

The new kernel option SX_NOINLINE can be used to disable the aforementioned
inlining in non-debug kernels.

The size of struct sx has changed, so the kernel ABI is probably greatly
disturbed.

MFC after: 1 month
Submitted by: attilio
Tested by: kris, pjd

Rename the 'mtx_object', 'rw_object', and 'sx_object' members of mutexes,
rwlocks, and sx locks to 'lock_object'.

Allow threads to atomically release rw and sx locks while waiting for an
event. Locking primitives that support this (mtx, rw, and sx) now each
include their own foo_sleep() routine.
- Rename msleep() to _sleep() and change it's 'struct mtx' object to a
'struct lock_object' pointer. _sleep() uses the recently added
lc_unlock() and lc_lock() function pointers for the lock class of the
specified lock to release the lock while the thread is suspended.
- Add wrappers around _sleep() for mutexes (mtx_sleep()), rw locks
(rw_sleep()), and sx locks (sx_sleep()). msleep() still exists and
is now identical to mtx_sleep(), but it is deprecated.
- Rename SLEEPQ_MSLEEP to SLEEPQ_SLEEP.
- Rewrite much of sleep.9 to not be msleep(9) centric.
- Flesh out the 'RETURN VALUES' section in sleep.9 and add an 'ERRORS'
section.
- Add __nonnull(1) to _sleep() and msleep_spin() so that the compiler will
warn if you try to pass a NULL wait channel. The functions already have
a KASSERT to that effect.

The _sx_assert() prototype should exist if either of INVARIANTS or
INVARIANT_SUPPORT is defined so you can build a kernel with
INVARIANT_SUPPORT, but build a module with just INVARIANTS on.

MFC after: 3 days
Reported by: kuriyama

Add a new 'show sleepchain' ddb command similar to 'show lockchain' except
that it operates on lockmgr and sx locks. This can be useful for tracking
down vnode deadlocks in VFS for example. Note that this command is a bit
more fragile than 'show lockchain' as we have to poke around at the
wait channel of a thread to see if it points to either a struct lock or
a condition variable inside of a struct sx. If td_wchan points to
something unmapped, then this command will terminate early due to a fault,
but no harm will be done.

Add a sx_xlocked() macro which returns true if the current thread holds an
exclusive lock on the specified sx lock.

Style fix.

Add a SYSUNINIT() to SX_SYSINIT() to call sx_destroy() to destroy the sx
lock when a module is unloaded similar to the recent change made to
MTX_SYSINIT().

Suggested by: pjd
MFC after: 3 days

/* -> /*- for license, minor formatting changes

Add sx_unlock() macro as a frontend to both sx_sunlock() and sx_xunlock(),
using sx_cnt to determine what state the lock is in and call the respective
function appropriately.

Include <sys/queue.h> before <sys/_lock.h> instead of depending on
namespace pollution in other headers. <sys/types.h> is now the only
prerequisite for <sys/sx.h>.

Fixed some style bugs:
- removed bogus LOCORE ifdef. Including this C header in assembler
sources is just nonsense.
- removed unused include of <sys/_mutex.h>. It finished rotting when
the mutex in struct sx became indirect in rev.1.15.
- removed most comments on #else and #endif's and cleaned up the others.
All were misindented...

Add SX_UNLOCKED define. It will be used with sx_assert(9) to be
sure that current thread does not hold given sx(9) lock.

Reviewed by: jhb
Approved by: jhb, scottl (mentor)

- Make this compile if INVARIANTS support is not enabled.

- Add MTX_SYSINIT and SX_SYSINIT as macro glue for allowing sx and mtx
locks to be able to setup a SYSINIT call. This helps in places where
a lock is needed to protect some data, but the data is not truly
associated with a subsystem that can properly initialize it's lock.
The macros use the mtx_sysinit() and sx_sysinit() functions,
respectively, as the handler argument to SYSINIT().

Reviewed by: alfred, jhb, smp@

Create a mutex pool API for short term leaf mutexes.
Replace the manual mutex pool in kern_lock.c (lockmgr locks) with the new API.
Replace the mutexes embedded in sxlocks with the new API.

Fix this to actually compile in the !INVARIANTS case.

Reported by: Maxime Henrion <mux@qualys.com>

Change the sx(9) assertion API to use a sx_assert() function similar to
mtx_assert(9) rather than several SX_ASSERT_* macros.

Use NULL instead of __FILE__ in the !LOCK_DEBUG case in the locking code
since the filenames are only used in the LOCK_DEBUG case and are just bloat
in the !LOCK_DEBUG case.

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

Include <sys/_lock.h> for the definition of struct lock_object. Don't
understand why this wasn't added when _mutex.h was added.

Noticed by: jlemon

Add sx_try_upgrade() and sx_downgrade().

Submitted by: Alexander Kabaev <ak03@gte.com>

- Add trylock variants of shared and exclusive locks.
- The sx assertions don't actually need the internal sx mutex lock, so
don't bother doing so.
- Add a new assertion SX_ASSERT_LOCKED() that asserts that either a
shared or exclusive lock should be held. This assertion should be used
instead of SX_ASSERT_SLOCKED() in almost all cases.
- Adjust some KASSERT()'s to include file and line information.
- Use the new witness_assert() function in the WITNESS case for sx slock
asserts to verify that the current thread actually owns a slock.

Undo part of the tangle of having sys/lock.h and sys/mutex.h included in
other "system" header files.

Also help the deprecation of lockmgr.h by making it a sub-include of
sys/lock.h and removing sys/lockmgr.h form kernel .c files.

Sort sys/*.h includes where possible in affected files.

OK'ed by: bde (with reservations)

Rework the witness code to work with sx locks as well as mutexes.
- Introduce lock classes and lock objects. Each lock class specifies a
name and set of flags (or properties) shared by all locks of a given
type. Currently there are three lock classes: spin mutexes, sleep
mutexes, and sx locks. A lock object specifies properties of an
additional lock along with a lock name and all of the extra stuff needed
to make witness work with a given lock. This abstract lock stuff is
defined in sys/lock.h. The lockmgr constants, types, and prototypes have
been moved to sys/lockmgr.h. For temporary backwards compatability,
sys/lock.h includes sys/lockmgr.h.
- Replace proc->p_spinlocks with a per-CPU list, PCPU(spinlocks), of spin
locks held. By making this per-cpu, we do not have to jump through
magic hoops to deal with sched_lock changing ownership during context
switches.
- Replace proc->p_heldmtx, formerly a list of held sleep mutexes, with
proc->p_sleeplocks, which is a list of held sleep locks including sleep
mutexes and sx locks.
- Add helper macros for logging lock events via the KTR_LOCK KTR logging
level so that the log messages are consistent.
- Add some new flags that can be passed to mtx_init():
- MTX_NOWITNESS - specifies that this lock should be ignored by witness.
This is used for the mutex that blocks a sx lock for example.
- MTX_QUIET - this is not new, but you can pass this to mtx_init() now
and no events will be logged for this lock, so that one doesn't have
to change all the individual mtx_lock/unlock() operations.
- All lock objects maintain an initialized flag. Use this flag to export
a mtx_initialized() macro that can be safely called from drivers. Also,
we on longer walk the all_mtx list if MUTEX_DEBUG is defined as witness
performs the corresponding checks using the initialized flag.
- The lock order reversal messages have been improved to output slightly
more accurate file and line numbers.

In order to avoid recursing on the backing mutex for sx locks in the
INVARIANTS case, define the actual KASSERT() in _SX_ASSERT_[SX]LOCKED
macros that are used in the sx code itself and convert the
SX_ASSERT_[SX]LOCKED macros to simple wrappers that grab the mutex for the
duration of the check.

Get the arguments to the KASSERT() printf() in SX_ASSERT_XLOCKED() in
the proper order.

Fix typo: define SX_ASSERT_XLOCKED not SX_ASSERT_XLOCKER in
non-INVARIANTS case.

PR: 25567
Submitted by: nnd@mail.nsk.ru

- Add sx_descr description member to sx lock structure
- Add sx_xholder member to sx struct which is used for INVARIANTS-enabled
assertions. It indicates the thread that presently owns the xlock.
- Add some assertions to the sx lock code that will detect the fatal
API abuse:
xlock --> xlock
xlock --> slock
which now works thanks to sx_xholder.
Notice that the remaining two problematic cases:
slock --> xlock
slock --> slock (a little less problematic, but still recursion)
will need to be handled by witness eventually, as they are more
involved.

Reviewed by: jhb, jake, jasone

Implement shared/exclusive locks.

Reviewed by: bmilekic, jake, jhb