dtrace sched:::preempt should fire only when there is preemption

The probe fire on any thread switch before.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Panzura

move thread switch tracing from mi_switch to sched_switch

This is done so that the thread state changes during the switch
are not confused with the thread state changes reported when the thread
spin

move thread switch tracing from mi_switch to sched_switch

This is done so that the thread state changes during the switch
are not confused with the thread state changes reported when the thread
spins on a lock.

Here is an example, three consecutive entries for the same thread (from top to
bottom):

KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"sleep", attributes: prio:84, wmesg:"-", lockname:"(null)"
KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"spinning", attributes: lockname:"sched lock 1"
KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"running", attributes: none

The above trace could leave an impression that the final state of
the thread was "running".
After this change the sleep state will be reported after the "spinning"
and "running" states reported for the sched lock.

Reviewed by: jhb, markj
MFC after: 1 week
Sponsored by: Panzura
Differential Revision: https://reviews.freebsd.org/D9961

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Merge ^/head r313644 through r313895.

Introduce SCHEDULER_STOPPED_TD for use when the thread pointer was already read

Sprinkle in few places.

MFhead@r313243

Merge ^/head r312309 through r312623.

disambiguate msleep KASSERT diagnostics

Previously "panic: msleep" could happen for a few different reasons.
Break the KASSERTs out into individual cases to identify the failing
condition. Found dur

disambiguate msleep KASSERT diagnostics

Previously "panic: msleep" could happen for a few different reasons.
Break the KASSERTs out into individual cases to identify the failing
condition. Found during the investigation that resulted in r308288.

Reviewed by: kib, jhb
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D8604

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Don't spin in pause() during early boot for kthreads other than thread0.

pause() uses a spin loop to simulate a sleep during early boot. However,
we only need this for thread0 to get far enough in

Don't spin in pause() during early boot for kthreads other than thread0.

pause() uses a spin loop to simulate a sleep during early boot. However,
we only need this for thread0 to get far enough in the boot process to
enable timers (at which point pause() can sleep). For other kthreads,
sleeping in pause() is ok as the callout will be scheduled and will
eventually fire once thread0 initializes timers.

Tested by: Steven Kargl
Sleuthing by: markj
MFC after: 1 week
Sponsored by: Netflix

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Merge ^/head r308227 through r308490.

Remove remnants of the recursive sleep support. Instead assert that
we never try to sleep while the thread is on a sleepqueue.

Reviewed by: jhb
Tested by: pho
Sponsored by: The FreeBSD Foundation
M

Remove remnants of the recursive sleep support. Instead assert that
we never try to sleep while the thread is on a sleepqueue.

Reviewed by: jhb
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D8422

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Merge ^/head r305687 through r305890.

Renumber license clauses in sys/kern to avoid skipping #3

Get rid of struct proc p_sched and struct thread td_sched pointers.

p_sched is unused.

The struct td_sched is always co-allocated with the struct thread,
except for the thread0. Avoid useless indi

Get rid of struct proc p_sched and struct thread td_sched pointers.

p_sched is unused.

The struct td_sched is always co-allocated with the struct thread,
except for the thread0. Avoid useless indirection, instead calculate
td_sched location using simple pointer arithmetic in td_get_sched(9).
For thread0, which is statically allocated, create a structure to
emulate layout of the dynamic allocation.

Reviewed by: jhb (previous version)
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D6711

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Use DELAY() instead of _sleep() when SCHEDULER_STOPPED() is set inside
pause_sbt(). This allows pause() to continue working during a panic()
which is not invoking KDB. This is useful when debugging g

Use DELAY() instead of _sleep() when SCHEDULER_STOPPED() is set inside
pause_sbt(). This allows pause() to continue working during a panic()
which is not invoking KDB. This is useful when debugging graphics
drivers using the LinuxKPI.

Obtained from: kmacy @
MFC after: 1 week

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sys: extend use of the howmany() macro when available.

We have a howmany() macro in the <sys/param.h> header that is
convenient to re-use as it makes things easier to read.

MFH

Sponsored by: The FreeBSD Foundation

Rework handling of thread sleeps before timers are working.

Previously, calls to *sleep() and cv_*wait*() immediately returned during
early boot. Instead, permit threads that request a sleep withou

Rework handling of thread sleeps before timers are working.

Previously, calls to *sleep() and cv_*wait*() immediately returned during
early boot. Instead, permit threads that request a sleep without a
timeout to sleep as wakeup() works during early boot. Sleeps with
timeouts are harder to emulate without working timers, so just punt and
panic explicitly if any thread tries to use those before timers are
working. Any threads that depend on timeouts should either wait until
SI_SUB_KICK_SCHEDULER to start or they should use DELAY() until timers
are available.

Until APs are started earlier this should be a no-op as other kthreads
shouldn't get a chance to start running until after timers are working
regardless of when they were created.

Reviewed by: kib
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D5724

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Add td_swinvoltick to track last involuntary context switch

Expose in DDB via "show thread."

Reviewed by: markj
Sponsored by: EMC / Isilon Storage Division

Catch up with HEAD (r280229-r284686).

Merge from head

Merge ^/head r283596 through r283770.

Remove several write-only variables, all reported by the gcc 4.9
buildkernel run.

Some of them were write-only under some kernel options, e.g. variables
keeping values only used by CTR() macros. It

Remove several write-only variables, all reported by the gcc 4.9
buildkernel run.

Some of them were write-only under some kernel options, e.g. variables
keeping values only used by CTR() macros. It costs nothing to the
code readability and correctness to eliminate the warnings in those
cases too by removing the local cached values used only for
single-access.

Review: https://reviews.freebsd.org/D2665
Reviewed by: rodrigc
Looked at by: bjk
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

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MFH: r282615-r283655

Sponsored by: The FreeBSD Foundation

Merge sync of head

CALLOUT_MPSAFE has lost its meaning since r141428, i.e., for more than ten
years for head. However, it is continuously misused as the mpsafe argument
for callout_init(9). Deprecate the flag and cle

CALLOUT_MPSAFE has lost its meaning since r141428, i.e., for more than ten
years for head. However, it is continuously misused as the mpsafe argument
for callout_init(9). Deprecate the flag and clean up callout_init() calls
to make them more consistent.

Differential Revision: https://reviews.freebsd.org/D2613
Reviewed by: jhb
MFC after: 2 weeks

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