kthread: Set *tdptr earlier in kproc_kthread_add()

See commit ae77041e0714 ("kthread: Set *newtdp earlier in
kthread_add1()") for details. That commit was incomplete since
g_init()'s first call to kproc_kthread_add() will cause
kproc_kthread_add() to take the `*procptr == NULL` branch, which avoids
kthread_create().

To ensure that the thread pointer is initialized before the thread
starts running, we have to start the kernel process with RFSTOPPED.
We could perhaps go further and use RFSTOPPED only when tdptr != NULL,
but it's probably better to have consistent behaviour.

Reviewed by: olce, kib
Reported by: syzbot+e91e798f3c088215ace6@syzkaller.appspotmail.com
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D44927

kthread: Set *newtdp earlier in kthread_add1()

syzbot reported a single boot-time crash in g_event_procbody(), a page
fault when dereferencing g_event_td. g_event_td is initialized by the
kproc_kthread_add() call which creates the GEOM event thread:

kproc_kthread_add(g_event_procbody, NULL, &g_proc, &g_event_td,
RFHIGHPID, 0, "geom", "g_event");

I believe that the caller of kproc_kthread_add() was preempted after
adding the new thread to the scheduler, and before setting *newtdp,
which is equal to g_event_td. Thus, since the first action of the GEOM
event thread is to lock itself, it ended up dereferencing a NULL
pointer.

Fix the problem simply by initializing *newtdp earlier. I see no harm
in that, and it matches kproc_create1(). The scheduler provides
sufficient synchronization to ensure that the store is visible to the
new thread, wherever it happens to run.

Reported by: syzbot+5397f4d39219b85a9409@syzkaller.appspotmail.com
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D42986

sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

kthread_add(): do not allow to attach the thread to a dead or dying process

Reported by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

kern_kthread: fork1() does not handle locked Giant

fork1() does not behave if called under Giant. For instance, it might
need to call thread_suspend_check() which explicitly verifies that Giant
is not locked. On the other hand, the kthread KPI is often called from
SYSINIT() which is still Giant-locked.

Correct this by dropping Giant in kthread_add() and kproc_create().

Reported by: pho
Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D41694

kern_kthread.c: some style

Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D41694

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

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

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

Update comments referencing create_thread()

The equivalent function is now named thread_create(). Mention
kthread_add() where it is also relevant.

Reviewed by: kib, markj
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38180

umtx: Split umtx.h on two counterparts.

To prevent umtx.h polluting by future changes split it on two headers:
umtx.h - ABI header for userspace;
umtxvar.h - the kernel staff.

While here fix umtx_key_match style.

Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D31248
MFC after: 2 weeks

Set TDP_KTHREAD before calling cpu_fork() and cpu_copy_thread().

This permits these routines to use special logic for initializing MD
kthread state.

For the kproc case, this required moving the logic to set these flags
from kproc_create() into do_fork().

Reviewed by: kib
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D29207

Provide ABI modules hooks for process exec/exit and thread exit.

Exec and exit are same as corresponding eventhandler hooks.

Thread exit hook is called somewhat earlier, while thread is still
owned by the process and enough context is available. Note that the
process lock is owned when the hook is called.

Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D27309

thread: rework tidhash vs proc lock interaction

Apart from minor clean up this gets rid of proc unlock/lock cycle on thread
exit to work around LOR against tidhash lock.

Do a lockless check in kthread_suspend_check

Otherwise an idle system running lockstat sleep 10 reports contention on
process lock comming from bufdaemon.

While here fix a style nit.

Remove duplicated empty lines from kern/*.c

No functional changes.

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

proc: always store parent pid in p_oppid

Doing so removes the dependency on proctree lock from sysctl process list
export which further reduces contention during poudriere -j 128 runs.

Reviewed by: kib (previous version)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17825

hwpmc: log name->pid, name->tid mappings

By logging all threads and processes 'pmc filter'
can now filter on process or thread name, relieving
the user of the burden of determining which tid or
pid was which when the sample was taken.

% pmc filter -T if_io_tqg -P nginx pmc.log pmc-iflib.log

% pmc filter -x -T idle pmc.log pmc-noidle.log

Implement several enhancements to NUMA policies.

Add a new "interleave" allocation policy which stripes pages across
domains with a stride or width keeping contiguity within a multi-page
region.

Move the kernel to the dedicated numbered cpuset #2 making it possible
to assign kernel threads and memory policy separately from user. This
also eliminates the need for the complicated interrupt binding code.

Add a sysctl API for viewing and manipulating domainsets. Refactor some
of the cpuset_t manipulation code using the generic bitset type so that
it can be used for both. This probably belongs in a dedicated subr file.

Attempt to improve the include situation.

Reviewed by: kib
Discussed with: jhb (cpuset parts)
Tested by: pho (before review feedback)
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14839

Instrument thread creations for the the benefit of the TSLOG framework.
This assists in tracking time spent while the boot is being "held" waiting
for something to happen.

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.

Re-schedule signals after kthread exits, since apparently there are
processes which combine kernel and non-kernel threads, e.g. nfsd. For
such processes, termination of a kthread must recheck signal delivery
among other threads according to masks.

Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Update comments for the MD functions managing contexts for new
threads, to make it less confusing and using modern kernel terms.

Rename the functions to reflect current use of the functions, instead
of the historic KSE conventions:
cpu_set_fork_handler -> cpu_fork_kthread_handler (for kthreads)
cpu_set_upcall -> cpu_copy_thread (for forks)
cpu_set_upcall_kse -> cpu_set_upcall (for new threads creation)

Reviewed by: jhb (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Approved by: re (hrs)
Differential revision: https://reviews.freebsd.org/D6731

kern: for pointers replace 0 with NULL.

These are mostly cosmetical, no functional change.

Found with devel/coccinelle.

Rename P_KTHREAD struct proc p_flag to P_KPROC.

I left as is an apparent bug in ntoskrnl_var.h:AT_PASSIVE_LEVEL()
definition.

Suggested by: jhb
Sponsored by: The FreeBSD Foundation

fork: pass arguments to fork1 in a dedicated structure

Suggested by: kib

Limit rights on process descriptors.

On CloudABI, the rights bits returned by cap_rights_get() match up with
the operations that you can actually perform on the file descriptor.

Limiting the rights is good, because it makes it easier to get uniform
behaviour across different operating systems. If process descriptors on
FreeBSD would suddenly gain support for any new file operation, this
wouldn't become exposed to CloudABI processes without first extending
the rights.

Extend fork1() to gain a 'struct filecaps' argument that allows you to
construct process descriptors with custom rights. Use this in
cloudabi_sys_proc_fork() to limit the rights to just fstat() and
pdwait().

Obtained from: https://github.com/NuxiNL/freebsd

The si_status field of the siginfo_t, provided by the waitid(2) and
SIGCHLD signal, should keep full 32 bits of the status passed to the
_exit(2).

Split the combined p_xstat of the struct proc into the separate exit
status p_xexit for normal process exit, and signalled termination
information p_xsig. Kernel-visible macro KW_EXITCODE() reconstructs
old p_xstat from p_xexit and p_xsig. p_xexit contains complete status
and copied out into si_status.

Requested by: Joerg Schilling
Reviewed by: jilles (previous version), pho
Tested by: pho
Sponsored by: The FreeBSD Foundation

Ansify another function. This is the last in the file, I hope.

ANSIfy the only function that uses K&R definition in this file.

Generalised support for copy-on-write structures shared by threads.

Thread credentials are maintained as follows: each thread has a pointer to
creds and a reference on them. The pointer is compared with proc's creds on
userspace<->kernel boundary and updated if needed.

This patch introduces a counter which can be compared instead, so that more
structures can use this scheme without adding more comparisons on the boundary.

The umtx_lock mutex is used by top-half of the kernel, but is
currently a spin lock. Apparently, the only reason for this is that
umtx_thread_exit() is called under the process spinlock, which put the
requirement on the umtx_lock. Note that the witness static order list
is wrong for the umtx_lock, umtx_lock is explicitely before any thread
lock, so it is also before sleepq locks.

Change umtx_lock to be the sleepable mutex. For the reason above, the
calls to umtx_thread_exit() are moved from thread_exit() earlier in
each caller, when the process spin lock is not yet taken.

Discussed with: jhb
Tested by: pho (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks

Do not use potentially stale thread in kthread_add()

When an existing process is provided, the thread selected to use
to initialize the new thread could have exited and be reaped.
Acquire the proc lock earlier to ensure the thread remains valid.

Reviewed by: jhb, julian (previous version)
MFC after: 3 days

Stop treating td_sigmask specially for the purposes of new thread
creation. Move it into the copied region of the struct thread.

Update some comments.

Requested by: bde
X-MFC after: never

Revert previous revision, misunderstood the code :(

Release proc lock after setting signal queue.

PR: kern/167727
Submitted by: Jinjun Gao <gjinjun gmail com>
MFC after: 2 weeks

Add a new sched_clear_name() method to the scheduler interface to clear
the cached name used for KTR_SCHED traces when a thread's name changes.
This way KTR_SCHED traces (and thus schedgraph) will notice when a thread's
name changes, most commonly via execve().

MFC after: 2 weeks

Whenever a new kernel thread is spawned, explicitly clear any CPU affinity
set on the new thread. This prevents the thread from inadvertently
inheriting affinity from a random sibling.

Submitted by: attilio
Tested by: pho
MFC after: 1 week

Add experimental support for process descriptors

A "process descriptor" file descriptor is used to manage processes
without using the PID namespace. This is required for Capsicum's
Capability Mode, where the PID namespace is unavailable.

New system calls pdfork(2) and pdkill(2) offer the functional equivalents
of fork(2) and kill(2). pdgetpid(2) allows querying the PID of the remote
process for debugging purposes. The currently-unimplemented pdwait(2) will,
in the future, allow querying rusage/exit status. In the interim, poll(2)
may be used to check (and wait for) process termination.

When a process is referenced by a process descriptor, it does not issue
SIGCHLD to the parent, making it suitable for use in libraries---a common
scenario when using library compartmentalisation from within large
applications (such as web browsers). Some observers may note a similarity
to Mach task ports; process descriptors provide a subset of this behaviour,
but in a UNIX style.

This feature is enabled by "options PROCDESC", but as with several other
Capsicum kernel features, is not enabled by default in GENERIC 9.0.

Reviewed by: jhb, kib
Approved by: re (kib), mentor (rwatson)
Sponsored by: Google Inc

- Properly initialize the base priority (td_base_pri) of thread0 to PVM
to match the desired priority in td_priority. Otherwise the first time
thread0 used a borrowed priority it would drop down to PUSER instead of
PVM.
- Explicitly initialize the starting priority of new kprocs to PVM to
avoid inheriting some random priority from thread0.

MFC after: 2 weeks

kproc_exit() is already marked __dead2 so a NOTREACHED comment here isn't
needed for lint.

Submitted by: bde

Small whitespace nits and add a comment explaining why kthread_exit() can
call kproc_exit() that was lost earlier.

In thr_exit() and kthread_exit(), only remove thread from
hash if it can directly exit, otherwise let exit1() do it.
The change should be in r213950, but for unknown reason,
it was lost.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create a global thread hash table to speed up thread lookup, use
rwlock to protect the table. In old code, thread lookup is done with
process lock held, to find a thread, kernel has to iterate through
process and thread list, this is quite inefficient.
With this change, test shows in extreme case performance is
dramatically improved.

Earlier patch was reviewed by: jhb, julian

Allow a const char * to be passed as the process name to kproc_kthread_add()
without generating a warning.

MFC after: 1 month

MFC r207468:
Extract thread_lock()/ruxagg()/thread_unlock() fragment into utility
function ruxagg_tlock().
Convert the definition of kern_getrusage() to ANSI C.

MFC r207602:
Implement RUSAGE_THREAD. Add td_rux to keep extended runtime and ticks
information for thread to allow calcru1() (re)use.

Rename ruxagg()->ruxagg_locked(), ruxagg_tlock()->ruxagg() [1].
The ruxagg_locked() function no longer clears thread ticks nor
td_incruntime.

Not an MFC: the td_rux is added to the end of struct thread to keep
the KBI. Explicit bzero() of td_rux is added to new thread initialization
points.

Use the cached value within comparison.

Submitted by: jhb

Fix the grammar.

Submitted by: Brandon Gooch <bgooch at se dot edu>

Fix a race in regard of p_numthreads.

Submitted by: Giovanni Trematerra
<giovanni dot trematerra at gmail dot com>

- Fix the kthread_{suspend, resume, suspend_check}() locking.
In the current code, the locking is completely broken and may lead
easilly to deadlocks. Fix it by using the proc_mtx, linked to the
suspending thread, as lock for the operation. Keep using the
thread_lock for setting and reading the flag even if it is not entirely
necessary (atomic ops may do it as well, but this way the code is more
readable).
- Fix a deadlock within kthread_suspend().
The suspender should not sleep on a different channel wrt the suspended
thread, or, otherwise, the awaker should wakeup both. Uniform the
interface to what the kproc_* counterparts do (sleeping on the same
channel).
- Change the kthread_suspend_check() prototype.
kthread_suspend_check() always assumes curthread and must only refer to
it, so skip the thread pointer as it may be easilly mistaken.
If curthread is not a kthread, the system will panic.

In collabouration with: jhb
Tested by: Giovanni Trematerra
<giovanni dot trematerra at gmail dot com>
MFC: 2 weeks

MFC r196730:
Remove the altkstacks, instead instantiate threads with kernel stack
allocated with the right size from the start. For the thread that has
kernel stack cached, verify that requested stack size is equial to the
actual, and reallocate the stack if sizes differ.

Introduce separate kernel stack cache that keeps some limited amount of
preallocated kernel stacks to lower the latency of thread allocation.

Not a merge: instead of removing td_altkstack* members of struct thread,
replace them with placeholders to keep struct thread layout on the
stable branch.

Also, record r196640, r196644 and r196648 as merged.

Approved by: re (kensmith)

Reintroduce the r196640, after fixing the problem with my testing.

Remove the altkstacks, instead instantiate threads with kernel stack
allocated with the right size from the start. For the thread that has
kernel stack cached, verify that requested stack size is equial to the
actual, and reallocate the stack if sizes differ [1].

This fixes the bug introduced by r173361 that was committed several days
after r173004 and consisted of kthread_add(9) ignoring the non-default
kernel stack size.

Also, r173361 removed the caching of the kernel stacks for a non-first
thread in the process. Introduce separate kernel stack cache that keeps
some limited amount of preallocated kernel stacks to lower the latency
of thread allocation. Add vm_lowmem handler to prune the cache on
low memory condition. This way, system with reasonable amount of the
threads get lower latency of thread creation, while still not exhausting
significant portion of KVA for unused kstacks.

Submitted by: peter [1]
Discussed with: jhb, julian, peter
Reviewed by: jhb
Tested by: pho (and retested according to new test scenarious)
MFC after: 1 week

Reverse r196640 and r196644 for now.

Remove the altkstacks, instead instantiate threads with kernel stack
allocated with the right size from the start. For the thread that has
kernel stack cached, verify that requested stack size is equial to the
actual, and reallocate the stack if sizes differ [1].

This fixes the bug introduced by r173361 that was committed several days
after r173004 and consisted of kthread_add(9) ignoring the non-default
kernel stack size.

Also, r173361 removed the caching of the kernel stacks for a non-first
thread in the process. Introduce separate kernel stack cache that keeps
some limited amount of preallocated kernel stacks to lower the latency
of thread allocation. Add vm_lowmem handler to prune the cache on
low memory condition. This way, system with reasonable amount of the
threads get lower latency of thread creation, while still not exhausting
significant portion of KVA for unused kstacks.

Submitted by: peter [1]
Discussed with: jhb, julian, peter
Reviewed by: jhb
Tested by: pho
MFC after: 1 week

- Import the HEAD csup code which is the basis for the cvsmode work.

Kill a dead variable

PR: 126223
Submitted by: Mateusz Guzik

Document the kproc_kthread_add() call
and fix a small detail of its implementation.
MFC after: 1 week

- Relax requirements for p_numthreads, p_threads, p_swtick, and p_nice from
requiring the per-process spinlock to only requiring the process lock.
- Reflect these changes in the proc.h documentation and consumers throughout
the kernel. This is a substantial reduction in locking cost for these
fields and was made possible by recent changes to threading support.

Acquire the process mutex and spin locks before calling thread_exit() in
kthread_exit() to fix panics when using INVARIANTS.

Add support for the pre-exisiting module shutdoen handshake.
Fix some comments.

If kthread_exit() is called on the last kthread in a kproc, then
all the work in kproc_exit must be done.
We don't actually have a user of this yet but why leave it to chance.

kthread_exit needs no stinkin argument.

Introduce a way to make pure kernal threads.
kthread_add() takes the same parameters as the old kthread_create()
plus a pointer to a process structure, and adds a kernel thread
to that process.

kproc_kthread_add() takes the parameters for kthread_add,
plus a process name and a pointer to a pointer to a process instead of just
a pointer, and if the proc * is NULL, it creates the process to the
specifications required, before adding the thread to it.

All other old kthread_xxx() calls return, but act on (struct thread *)
instead of (struct proc *). One reason to change the name is so that
any old kernel modules that are lying around and expect kthread_create()
to make a process will not just accidentally link.

fix top to show kernel threads by their thread name in -SH mode
add a tdnam formatting option to ps to show thread names.

make all idle threads actual kthreads and put them into their own idled process.
make all interrupt threads kthreads and put them in an interd process
(mainly for aesthetic and accounting reasons)
rename proc 0 to be 'kernel' and it's swapper thread is now 'swapper'

man page fixes to follow.

Rename the kthread_xxx (e.g. kthread_create()) calls
to kproc_xxx as they actually make whole processes.
Thos makes way for us to add REAL kthread_create() and friends
that actually make theads. it turns out that most of these
calls actually end up being moved back to the thread version
when it's added. but we need to make this cosmetic change first.

I'd LOVE to do this rename in 7.0 so that we can eventually MFC the
new kthread_xxx() calls.

Commit 14/14 of sched_lock decomposition.
- Use thread_lock() rather than sched_lock for per-thread scheduling
sychronization.
- Use the per-process spinlock rather than the sched_lock for per-process
scheduling synchronization.

Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)

- Remove setrunqueue and replace it with direct calls to sched_add().
setrunqueue() was mostly empty. The few asserts and thread state
setting were moved to the individual schedulers. sched_add() was
chosen to displace it for naming consistency reasons.
- Remove adjustrunqueue, it was 4 lines of code that was ifdef'd to be
different on all three schedulers where it was only called in one place
each.
- Remove the long ifdef'd out remrunqueue code.
- Remove the now redundant ts_state. Inspect the thread state directly.
- Don't set TSF_* flags from kern_switch.c, we were only doing this to
support a feature in one scheduler.
- Change sched_choose() to return a thread rather than a td_sched. Also,
rely on the schedulers to return the idlethread. This simplifies the
logic in choosethread(). Aside from the run queue links kern_switch.c
mostly does not care about the contents of td_sched.

Discussed with: julian

- Move the idle thread loop into the per scheduler area. ULE wants to
do something different from the other schedulers.

Suggested by: jhb

Tested on: x86/amd64 sched_{4BSD, ULE, CORE}.

Don't do a PHOLD() in kthread_create() w/o a matching PRELE() in
kthread_exit(). Rather than add the missing PRELE() I chose to just
axe the PHOLD() since it was redundant with the P_SYSTEM flag.

MFC after: 1 week

- Move the wakeup() for exiting kthreads out of exit1() and into
kthread_exit() as that is cleaner and less obscured. It also does the
wakeup sooner.
- Add some comments to kthread_exit().

/* -> /*- for copyright notices, minor format tweaks as necessary

Give setrunqueue() and sched_add() more of a clue as to
where they are coming from and what is expected from them.

MFC after: 2 days

Use __FBSDID().

- Merge struct procsig with struct sigacts.
- Move struct sigacts out of the u-area and malloc() it using the
M_SUBPROC malloc bucket.
- Add a small sigacts_*() API for managing sigacts structures: sigacts_alloc(),
sigacts_free(), sigacts_copy(), sigacts_share(), and sigacts_shared().
- Remove the p_sigignore, p_sigacts, and p_sigcatch macros.
- Add a mutex to struct sigacts that protects all the members of the struct.
- Add sigacts locking.
- Remove Giant from nosys(), kill(), killpg(), and kern_sigaction() now
that sigacts is locked.
- Several in-kernel functions such as psignal(), tdsignal(), trapsignal(),
and thread_stopped() are now MP safe.

Reviewed by: arch@
Approved by: re (rwatson)

Instead of recording the Unix time in a process when it starts, record the
uptime. Where necessary, convert it back to Unix time by adding boottime
to it. This fixes a potential problem in the accounting code, which would
compute the elapsed time incorrectly if the Unix time was stepped during
the lifetime of the process.

fork1() already sets PS_INMEM, so don't set it again. This lets us push
sched_lock down slightly so that it isn't needed in the RFSTOPPED case.

Some kernel threads try to do significant work, and the default KSTACK_PAGES
doesn't give them enough stack to do much before blowing away the pcb.
This adds MI and MD code to allow the allocation of an alternate kstack
who's size can be speficied when calling kthread_create. Passing the
value 0 prevents the alternate kstack from being created. Note that the
ia64 MD code is missing for now, and PowerPC was only partially written
due to the pmap.c being incomplete there.
Though this patch does not modify anything to make use of the alternate
kstack, acpi and usb are good candidates.

Reviewed by: jake, peter, jhb

Back our kernel support for reliable signal queues.

Requested by: rwatson, phk, and many others

First half of implementation of ksiginfo, signal queues, and such. This
gets signals operating based on a TailQ, and is good enough to run X11,
GNOME, and do job control. There are some intricate parts which could be
more refined to match the sigset_t versions, but those require further
evaluation of directions in which our signal system can expand and contract
to fit our needs.

After this has been in the tree for a while, I will make in kernel API
changes, most notably to trapsignal(9) and sendsig(9), to use ksiginfo
more robustly, such that we can actually pass information with our
(queued) signals to the userland. That will also result in using a
struct ksiginfo pointer, rather than a signal number, in a lot of
kern_sig.c, to refer to an individual pending signal queue member, but
right now there is no defined behaviour for such.

CODAFS is unfinished in this regard because the logic is unclear in
some places.

Sponsored by: New Gold Technology
Reviewed by: bde, tjr, jake [an older version, logic similar]

Completely redo thread states.

Reviewed by: davidxu@freebsd.org

Part 1 of KSE-III

The ability to schedule multiple threads per process
(one one cpu) by making ALL system calls optionally asynchronous.
to come: ia64 and power-pc patches, patches for gdb, test program (in tools)

Reviewed by: Almost everyone who counts
(at various times, peter, jhb, matt, alfred, mini, bernd,
and a cast of thousands)

NOTE: this is still Beta code, and contains lots of debugging stuff.
expect slight instability in signals..

Fix a couple of style bugs introduced (or touched by) previous commit.

Pre-KSE/M3 commit.
this is a low-functionality change that changes the kernel to access the main
thread of a process via the linked list of threads rather than
assuming that it is embedded in the process. It IS still embeded there
but remove all teh code that assumes that in preparation for the next commit
which will actually move it out.

Reviewed by: peter@freebsd.org, gallatin@cs.duke.edu, benno rice,

Use a different mechanism to get the vnlru process to wake up and notice
the shutdown request at reboot/halt time.
Disable the printf 'vnlru process getting nowhere, pausing...' and instead
export the count to the debug.vnlru_nowhere sysctl.

Commit the better version that I had a while ago. This has only one
reference to curthread. (#define curproc (curthread->td_proc)).

When curproc is used repeatedly store curproc into a local
variable to reduce generated code. This is a test case.

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

Don't use kp->arg0 as a format string, grr.

MFC after: 1 week

Convert the allproc and proctree locks from lockmgr locks to sx locks.

- Use _PHOLD and move it before a PROC_UNLOCK to reduce the number of
mutex operations in kthread_create().
- Lock a kthread's proc before changing its parent via proc_reparent().
- Test P_KTHREAD not P_SYSTEM in kthread_suspend() and kthread_resume().
P_SYSTEM just means that the process shouldn't be swapped and is used
for vinum's daemon for example.
- Lock all the signal state used for suspending and resuming kthreads with
the proc lock.

Change and clean the mutex lock interface.

mtx_enter(lock, type) becomes:

mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)

similarily, for releasing a lock, we now have:

mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.

The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.

Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:

MTX_QUIET and MTX_NOSWITCH

The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:

mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.

Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.

Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.

Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.

Finally, caught up to the interface changes in all sys code.

Contributors: jake, jhb, jasone (in no particular order)

- Catch up to proc flag changes.
- Set the new P_KTHREAD flag for kthreads during kthread_create.

Protect proc.p_pptr and proc.p_children/p_sibling with the
proctree_lock.

linprocfs not locked pending response from informal maintainer.

Reviewed by: jhb, -smp@

Stick the kthread API in a kthread_* namespace, and the specialized kproc
functions in a kproc_* namespace.

Reviewed by: -arch

Pass RFSTOPPED to fork1() in kthread_create() to avoid a race condition
where fork1() could put the process on the run queue where it could be
snatched up by another CPU before kthread_create() had set the proper
fork handler. Instead, we put the new kthread on the runqueue after its
fork handler has been sent.

Noticed by: jake
Looked over by: peter

Reparent a kernel thread to init during kthread_exit() so that the zombie
can be reaped.

Major update to the way synchronization is done in the kernel. Highlights
include:

* Mutual exclusion is used instead of spl*(). See mutex(9). (Note: The
alpha port is still in transition and currently uses both.)

* Per-CPU idle processes.

* Interrupts are run in their own separate kernel threads and can be
preempted (i386 only).

Partially contributed by: BSDi (BSD/OS)
Submissions by (at least): cp, dfr, dillon, grog, jake, jhb, sheldonh

Clean up some low level bootstrap code:

- stop using the evil 'struct trapframe' argument for mi_startup()
(formerly main()). There are much better ways of doing it.
- do not use prepare_usermode() - setregs() in execve() will do it
all for us as long as the p_md.md_regs pointer is set. (which is
now done in machdep.c rather than init_main.c. The Alpha port did it
this way all along and is much cleaner).
- collect all the magic %cr0 etc register settings into one place and
have the AP's call that instead of using magic numbers (!!) that keep
changing over and over again.
- Make it safe to call kthread_create() earlier, including during the
device probe sequence. It doesn't need the callback mechanism that
NetBSD's version uses.
- kthreads created this way are root-less as they exist before the root
filesystem is mounted. init(1) is set up so that it aquires the root
pointers prior to running. If other kthreads want filesystem acccess
we can make this code more generic.
- set all threads start times once we have decided what time it is.
- init uses a trampoline rather than the evil prepare_usermode() hack.
- kern_descrip.c has a couple of tweaks to deal with forking when there
is no rootdir or cwd etc.
- adjust the early SYSINIT() sequence so that a few prereqisites are in
place. eg: make sure the run queue is initialized before doing forks.

With this, the USB code can easily create a kthread to do the device
tree discovery. (I have tested it, it works nicely).

There are still some open issues before this is truely useful.
- tsleep() does not like working before the clock is running. It
sort-of tries to spin wait, but it can do more useful things now.
- stopping a kthread in kld code at unload time is "interesting" but
we have a solution for that.

The Alpha code needs no changes for this. It already uses pretty much the
same strategies, but a little cleaner.

Panic if proc0 hasn't been created and we try to call kthread_create.
This prevents a more mysterious crash later.

XXX The long term solution is defer creation of these things until
XXX proc0 lives

Introduce a mechanism to suspend/resume system processes. Suspend syncer
and bufdaemon prior to disk sync during system shutdown.

Add a per-signal flag to mark handlers registered with osigaction, so we
can provide the correct context to each signal handler.

Fix broken sigsuspend(): don't use p_oldsigmask as a flag, use SAS_OLDMASK
as we did before the linuxthreads support merge (submitted by bde).

Move ps_sigstk from to p_sigacts to the main proc structure since signal
stack should not be shared among threads.

Move SAS_OLDMASK and SAS_ALTSTACK flags from sigacts::ps_flags to proc::p_flag.
Move PS_NOCLDSTOP and PS_NOCLDWAIT flags from proc::p_flag to procsig::ps_flag.

Reviewed by: marcel, jdp, bde

Trim unused options (or #ifdef for undoc options).

Submitted by: phk

Slight reorganization of kernel thread/process creation. Instead of using
SYSINIT_KT() etc (which is a static, compile-time procedure), use a
NetBSD-style kthread_create() interface. kproc_start is still available
as a SYSINIT() hook. This allowed simplification of chunks of the
sysinit code in the process. This kthread_create() is our old kproc_start
internals, with the SYSINIT_KT fork hooks grafted in and tweaked to work
the same as the NetBSD one.

One thing I'd like to do shortly is get rid of nfsiod as a user initiated
process. It makes sense for the nfs client code to create them on the
fly as needed up to a user settable limit. This means that nfsiod
doesn't need to be in /sbin and is always "available". This is a fair bit
easier to do outside of the SYSINIT_KT() framework.