turnstile: Mention the lock name when panicking due to a sleeping thread

This will hopefully make it a bit easier to track down the cause of such
panics.

MFC after: 2 weeks

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

ddb: Always terminate DB_SHOW_ALIAS_FLAGS with a semi-colon.

Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D40818

ddb: annotate some commands with DB_CMD_MEMSAFE

This is not completely exhaustive, but covers a large majority of
commands in the tree.

Reviewed by: markj
Sponsored by: Juniper Networks, Inc.
Spons

ddb: annotate some commands with DB_CMD_MEMSAFE

This is not completely exhaustive, but covers a large majority of
commands in the tree.

Reviewed by: markj
Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D35583

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Use atomic loads/stores when updating td->td_state

KCSAN complains about racy accesses in the locking code. Those races are
fine since they are inside a TD_SET_RUNNING() loop that expects the value

Use atomic loads/stores when updating td->td_state

KCSAN complains about racy accesses in the locking code. Those races are
fine since they are inside a TD_SET_RUNNING() loop that expects the value
to be changed by another CPU.

Use relaxed atomic stores/loads to indicate that this variable can be
written/read by multiple CPUs at the same time. This will also prevent
the compiler from doing unexpected re-ordering.

Reported by: GENERIC-KCSAN
Test Plan: KCSAN no longer complains, kernel still runs fine.
Reviewed By: markj, mjg (earlier version)
Differential Revision: https://reviews.freebsd.org/D28569

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kern: clean up empty lines in .c and .h files

ddb(4): show lockchain: Don't dereference LK_KERNPROC

Also, print a little more information for otherwise unhandled inhibited states.

Finally, improve the grammar of some prints. Some of the print

ddb(4): show lockchain: Don't dereference LK_KERNPROC

Also, print a little more information for otherwise unhandled inhibited states.

Finally, improve the grammar of some prints. Some of the print statements
missing verb.

Sponsored by: Dell EMC Isilon

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Merge ^/head r358269 through r358399.

Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (17 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly mark

Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (17 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all obvious cases as MPSAFE. All entries that haven't been marked
as MPSAFE before are by default marked as NEEDGIANT

Approved by: kib (mentor, blanket)
Commented by: kib, gallatin, melifaro
Differential Revision: https://reviews.freebsd.org/D23718

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schedlock 4/4

Don't hold the scheduler lock while doing context switches. Instead we
unlock after selecting the new thread and switch within a spinlock
section leaving interrupts and preemption dis

schedlock 4/4

Don't hold the scheduler lock while doing context switches. Instead we
unlock after selecting the new thread and switch within a spinlock
section leaving interrupts and preemption disabled to prevent local
concurrency. This means that mi_switch() is entered with the thread
locked but returns without. This dramatically simplifies scheduler
locking because we will not hold the schedlock while spinning on
blocked lock in switch.

This change has not been made to 4BSD but in principle it would be
more straightforward.

Discussed with: markj
Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22778

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schedlock 3/4

Eliminate lock recursion from turnstiles. This was simply used to avoid
tracking the top-level turnstile lock. explicitly check for it before
picking up and dropping locks.

Reviewed

schedlock 3/4

Eliminate lock recursion from turnstiles. This was simply used to avoid
tracking the top-level turnstile lock. explicitly check for it before
picking up and dropping locks.

Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22746

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schedlock 1/4

Eliminate recursion from most thread_lock consumers. Return from
sched_add() without the thread_lock held. This eliminates unnecessary
atomics and lock word loads as well as reducing

schedlock 1/4

Eliminate recursion from most thread_lock consumers. Return from
sched_add() without the thread_lock held. This eliminates unnecessary
atomics and lock word loads as well as reducing the hold time for
scheduler locks. This will eventually allow for lockless remote adds.

Discussed with: kib
Reviewed by: jhb
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22626

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MFHead @r350386

Sponsored by: The FreeBSD Foundation

Fix the turnstile_lock() KPI.

turnstile_{lock,unlock}() were added for use in epoch. turnstile_lock()
returned NULL to indicate that the calling thread had lost a race and
the turnstile was no long

Fix the turnstile_lock() KPI.

turnstile_{lock,unlock}() were added for use in epoch. turnstile_lock()
returned NULL to indicate that the calling thread had lost a race and
the turnstile was no longer associated with the given lock, or the lock
owner. However, reader-writer locks may not have a designated owner,
in which case turnstile_lock() would return NULL and
epoch_block_handler_preempt() would leak spinlocks as a result.

Apply a minimal fix: return the lock owner as a separate return value.

Reviewed by: kib
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21048

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MFHead @348740

Sponsored by: The FreeBSD Foundation

subr_turnstile: Extract some common code to a helper.

Code walks the list of contested turnstiles to calculate the priority
to unlend.

Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD F

subr_turnstile: Extract some common code to a helper.

Code walks the list of contested turnstiles to calculate the priority
to unlend.

Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

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Remove an unused argument to turnstile_unpend.

PR: 228694
Submitted by: Julian Pszczołowski <julian.pszczolowski@gmail.com>

turnstile / sleepqueue: annotate variables only used by debug builds

Add simple preempt safe epoch API

Read locking is over used in the kernel to guarantee liveness. This API makes
it easy to provide livenes guarantees without atomics.

Includes epoch_test kernel mod

Add simple preempt safe epoch API

Read locking is over used in the kernel to guarantee liveness. This API makes
it easy to provide livenes guarantees without atomics.

Includes epoch_test kernel module to stress test the API.

Documentation will follow initial use case.

Test case and improvements to preemption handling in response to discussion
with mjg@

Reviewed by: imp@, shurd@
Approved by: sbruno@

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sys/kern: adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone

sys/kern: adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

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MFH @ r323558.

MFhead@r322870

Remove unused declaration and update ddb.4

A follow-up to r322836.

Warnings for the unused declaration were breaking some second tier
architectures, but did not show up in Clang on x86.

Reported b

Remove unused declaration and update ddb.4

A follow-up to r322836.

Warnings for the unused declaration were breaking some second tier
architectures, but did not show up in Clang on x86.

Reported by: markj (ddb.4), emaste (declaration)
Sponsored by: Dell EMC Isilon

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Merge print_lockchain and print_sleepchain

When debugging a deadlock, it is useful to follow the full chain of locks as
far as possible.

Reviewed by: jhb
Sponsored by: Dell EMC Isilon
Differential

Merge print_lockchain and print_sleepchain

When debugging a deadlock, it is useful to follow the full chain of locks as
far as possible.

Reviewed by: jhb
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D12115

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Merge ^/head r307736 through r308146.