kern_reboot(9): belatedly bump .Dd

Fixes: 4e78a766f607 ("kern_reboot(): don't clear kdb_active")
Sponsored by: The FreeBSD Foundation

kern_reboot(): don't clear kdb_active

It is possible to reach this function from ddb via the "reset" command.
When this happens, we don't actually exit kdb, meaning we never execute
the latter steps

kern_reboot(): don't clear kdb_active

It is possible to reach this function from ddb via the "reset" command.
When this happens, we don't actually exit kdb, meaning we never execute
the latter steps of kdb_break() to restore the system state (e.g.
re-enable scheduler).

Therefore, we should not clear the kdb_active flag in this function, as
the debugger is still active. Put differently, kern_reboot() is not an
authority on kdb state, and should not touch it. The original motivation
for this assignment is not clear; I have checked thoroughly and I am
convinced it is not required by any reset code.

This fixes an edge case where a panic can be triggered during reset from
ddb:
1. Enter ddb via keyboard break sequence (KERNEL_PANICKED() == false &&
td->td_critnest > 0)
2. Execute the "reset" command
3. kern_reboot() sets kdb_active = false
4. A witness_checkorder() call via shutdown handler sees !kdb_active
and panics

Reviewed by: imp, markj
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D42684

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Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

kern_reboot(9): describe event handlers

Add more details about the execution and purpose of these shutdown
handlers. Make a point to mention the requirement that they can be run
in a normal or panic

kern_reboot(9): describe event handlers

Add more details about the execution and purpose of these shutdown
handlers. Make a point to mention the requirement that they can be run
in a normal or panic context. Add some simple examples.

Add a brief comment to the declaration in sys/eventhandler.h.

Reviewed by: markj
Discussed with: rpokala, Pau Amma <pauamma@gundo.com>
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D39135

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kern_reboot(9): document shutdown_nice()

Reviewed by: markj, Pau Amma <pauamma@gundo.com>
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3

kern_reboot(9): document shutdown_nice()

Reviewed by: markj, Pau Amma <pauamma@gundo.com>
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D39134

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kern_reboot(9): some updates

- This function no longer disables interrupts
- MLINK to reboot.9
- The mentions of autoconfiguration is more about shutdown_nice(),
coming in the next commit.
-

kern_reboot(9): some updates

- This function no longer disables interrupts
- MLINK to reboot.9
- The mentions of autoconfiguration is more about shutdown_nice(),
coming in the next commit.
- Describe the RB_* flags relevant to this function
- Describe behaviour when shutdown hooks fail the reset
- Describe expected execution contexts
- Add FF copyright
- xref panic(9)
- xref this page in reboot(2)

Reviewed by: markj
Discussed with: rpokala, Pau Amma <pauamma@gundo.com>
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D39133

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Fix a slew of mdoc warnings/errors.

boot(9): update to match reality

This function was renamed to kern_reboot() in 2010, but the man page has
failed to keep in sync. Bring it up to date on the rename, add the
shutdown hooks to the syn

boot(9): update to match reality

This function was renamed to kern_reboot() in 2010, but the man page has
failed to keep in sync. Bring it up to date on the rename, add the
shutdown hooks to the synopsis, and document the (obvious) fact that
kern_reboot() does not return.

Fix an outdated reference to the old name in kern_reboot(), and leave a
reference to the man page so future readers might find it before any
large changes.

Reviewed by: imp, markj
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D32085

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