MFC r255505:
  Do not install freebsd-update.conf.5 manual if WITHOUT_FREEBSD_UPDATE
  is set.

Sponsored by:	The FreeBSD Foundation
MFC r255356:

Revert parts of r245132 and r245175. We don't need to write to the
IMAN register to clear the pending interrupt status bits. This patch
tries to solve problems seen on the MacBook Air, as reported by
Johannes Lundberg <johannes@brilliantservice.co.jp>
MFC r255483:

Do not emit size for non-regular files.  There is nothing that
mtree(1) can do in this situation and would cause confusion.
MFC r248246:

- Make quirk for reading device descriptor from broken USB devices.
Else they won't enumerate at all:
hw.usb.full_ddesc=1
- Reduce the USB descriptor read timeout from 1000ms to
500ms. Typical value for LOW speed devices is 50-100ms.
- Enumerate USB device a maximum of 3 times when a port
connection change event is detected, before giving up.
MFC r254572:
Force keyboards which don't have the required
HID fields to use the USB BOOT protocol for now.

PR:		usb/181425
MFC r255235:
  Remove unused code and sort variables declarations.

PR:		kern/181822
MFC r255472:
Clear correct data structure.
MFC r248114 (by melifaro):

Add forgotten .El
MFC r255488:
Don't issue USB resume signalling in USB device mode, if the USB power
mode is ON and suspend is detected. This confuses iPads running in USB
host mode at least.
Merge from r245741 from head:

  If lagg(4) can't forward a packet due to underlying port problems,
  return much more meaningful ENETDOWN to the stack, instead of EBUSY.
MFC r255340:

Long URLs don't always appear even with autosizing and other tricks. So,
add some whitespace to put the URL on a line by itself, maximizing view.

MFC r255341:

Remove unnecessary mediaClose (FTP operations are done with either ftp(1)
or fetch(1), neither of which are stateful, compared to how sysinstall(8)
did FTP operations, maintaining an open session until mediaClose).
MFC r255509:
Reduce the scope of the proctree_lock.
MFC r255510:
When opening or closing fifo, ensure that the vnode is locked exclusively.
MFC r255527:
Use TAILQ instead of STAILQ for kqeueue filedescriptors to ensure constant
time removal on kqueue close.
MFC r254742:
Hold mfi_io_lock across calls to xpt_rescan() and xpt_alloc_ccb_nowait().
xpt_rescan() expects the SIM lock to be held, and we trip a mtx_assert if
the driver initiates multiple rescans in quick succession.
MFC r254467:
Remove a couple of unused macros.
MFC r250953:
The fasttrap provider cleans up probes asynchronously when a process with
USDT probes exits. This was previously done with a callout; however, it is
possible to sleep while holding the DTrace mutexes, so a panic will occur
on INVARIANTS kernels if the callout handler can't immediately acquire one
of these mutexes. This panic will be frequently triggered on systems where
a USDT-enabled program (perl, for instance) is often run.

This revision changes the fasttrap cleanup mechanism so that a dedicated
thread is used instead of a callout. The old behaviour is otherwise
preserved.

MFC r252493:
Be sure to destory the fasttrap cleanup mutex when unloading the fasttrap
module. This should be MFCed with r250953.
MFC r252894:
Add SDT_PROBE_DEFINE0 for consistency with SDT_PROBE0.

MFC r253022:
Also define SDT_PROBE_DEFINE0 for the !KDTRACE_HOOKS case.

MFC r254266:
Add event handlers for module load and unload events. The load handlers are
called after the module has been loaded, and the unload handlers are called
before the module is unloaded. Moreover, the module unload handlers may
return an error to prevent the unload from proceeding.

MFC r254267:
Remove some unused fields from struct linker_file. They were added in
r172862 for use by the DTrace SDT framework but don't seem to have ever
been used.

MFC r254268:
FreeBSD's DTrace implementation has a few problems with respect to handling
probes declared in a kernel module when that module is unloaded. In
particular,

* Unloading a module with active SDT probes will cause a panic. [1]
* A module's (FBT/SDT) probes aren't destroyed when the module is unloaded;
  trying to use them after the fact will generally cause a panic.

This change fixes both problems by porting the DTrace module load/unload
handlers from illumos and registering them with the corresponding
EVENTHANDLER(9) handlers. This allows the DTrace framework to destroy all
probes defined in a module when that module is unloaded, and to prevent a
module unload from proceeding if some of its probes are active. The latter
problem has already been fixed for FBT probes by checking lf->nenabled in
kern_kldunload(), but moving the check into the DTrace framework generalizes
it to all kernel providers and also fixes a race in the current
implementation (since a probe may be activated between the check and the
call to linker_file_unload()).

Additionally, the SDT implementation has been reworked to define SDT
providers/probes/argtypes in linker sets rather than using SYSINIT/SYSUNINIT
to create and destroy SDT probes when a module is loaded or unloaded. This
simplifies things quite a bit since it means that pretty much all of the SDT
code can live in sdt.ko, and since it becomes easier to integrate SDT with
the DTrace framework. Furthermore, this allows FreeBSD to be quite flexible
in that SDT providers spanning multiple modules can be created on the fly
when a module is loaded; at the moment it looks like illumos' SDT
implementation requires all SDT probes to be statically defined in a single
kernel table.

MFC r254309:
Use kld_{load,unload} instead of mod_{load,unload} for the linker file load
and unload event handlers added in r254266.

MFC r254350:
Specify SDT probe argument types in the probe definition itself rather than
using SDT_PROBE_ARGTYPE(). This will make it easy to extend the SDT(9) API
to allow probes with dynamically-translated types.
MFC: r255216
Crashes have been observed for NFSv4.1 mounts when the system
is being shut down which were caused by the nfscbd_pool being
destroyed before the backchannel is disabled. This patch is
believed to fix the problem, by simply avoiding ever destroying
the nfscbd_pool. Since the NFS client module cannot be unloaded,
this should not cause a memory leak.
MFC: r255284
It was reported via email that the cu_sent field used by the
krpc client side UDP was observed as way out of range and
caused the rpc.lockd daemon to hang trying to do an RPC.
Inspection of the code found two places where the RPC request
is re-queued, but the value of cu_sent was not incremented.
Since cu_sent is always decremented when the RPC request is
dequeued, I think this could have caused cu_sent to go out of
range. This patch adds lines to increment cu_sent for these
two cases.