Merge from head

Sponsored by: Gandi.net

Sysctl: Add common support for U8, U16 types

Sponsored by: EMC / Isilon Storage Division

Merge from head

Merge from head

Sync up with head (up to r288341).

Merge ^/head r287680 through r287877.

sysctl: switch sysctllock to a sleepable rmlock, take 2

This restores r285125. Previous attempt was reverted due to a bug in rmlocks,
which is fixed since r287833.

Finish merging from head, messed up in previous attempt

Merge from head

Catch up with head, primarily for the 1.14.4.0 firmware.

Merge ^/head r285924 through r286421.

Revert r285125 until rmlocks get fixed.

Right now there is a chance that sysctl unregister will cause reader to
block on the sx lock associated with sysctl rmlock, in which case kernels
with debug e

Revert r285125 until rmlocks get fixed.

Right now there is a chance that sysctl unregister will cause reader to
block on the sx lock associated with sysctl rmlock, in which case kernels
with debug enabled will panic.

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Merge ^/head r285153 through r285283.

Don't acquire sysctlmemlock in userland_sysctl() when the old value
pointer is NULL, as in that case there are no userland pages that
could potentially be wired. It is common for old to be NULL and

Don't acquire sysctlmemlock in userland_sysctl() when the old value
pointer is NULL, as in that case there are no userland pages that
could potentially be wired. It is common for old to be NULL and
oldlenp to be non-NULL in calls to userland_sysctl(), as this is used
to probe for the length of a variable-length sysctl entry before
retrieving a value. Note that it is typical for such calls to be made
with an uninitialized value in *oldlenp, so sysctlmemlock was
essentially being acquired at random (depending on the uninitialized
value in *oldlenp being > PAGE_SIZE or not) for these calls prior to
this patch.

Differential Revision: https://reviews.freebsd.org/D2987
Reviewed by: mjg, kib
Approved by: jmallett (mentor)
MFC after: 1 month

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Merge ^/head r284737 through r285152.

sysctl: get rid of sysctl_lock/unlock

Inline their contents into the only consumer.

sysctl: remove a debugging printf which crept in with r285125

sysctl: switch sysctllock to a sleepable rmlock

The lock is almost never taken for writing.

Catch up with HEAD (r280229-r284686).

Merge sync of head

Merge from HEAD

MFH: r278968-r280640

Sponsored by: The FreeBSD Foundation

Implement a simple OID number garbage collector. Given the increasing
number of dynamically created and destroyed SYSCTLs during runtime it
is very likely that the current new OID number limit of 0x7

Implement a simple OID number garbage collector. Given the increasing
number of dynamically created and destroyed SYSCTLs during runtime it
is very likely that the current new OID number limit of 0x7fffffff can
be reached. Especially if dynamic OID creation and destruction results
from automatic tests. Additional changes:

- Optimize the typical use case by decrementing the next automatic OID
sequence number instead of incrementing it. This saves searching time
when inserting new OIDs into a fresh parent OID node.

- Add simple check for duplicate non-automatic OID numbers.

MFC after: 1 week

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Make sure tunable sysctls are only fetched once. The existing code can
re-register sysctls when destroying sysctl contexts or when moving
sysctls from one tree to another.

Correct string pointer offset for error printout.