system/kernel/thread.cpp

/*
 * Copyright 2002-2008, Axel Dörfler, axeld@pinc-software.de.
 * Distributed under the terms of the MIT License.
 *
 * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
 * Distributed under the terms of the NewOS License.
 */

/*! Threading routines */


#include <thread.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>

#include <OS.h>

#include <util/AutoLock.h>
#include <util/khash.h>

#include <arch/debug.h>
#include <boot/kernel_args.h>
#include <condition_variable.h>
#include <cpu.h>
#include <int.h>
#include <kimage.h>
#include <kscheduler.h>
#include <ksignal.h>
#include <smp.h>
#include <syscalls.h>
#include <syscall_restart.h>
#include <team.h>
#include <tls.h>
#include <user_runtime.h>
#include <vfs.h>
#include <vm.h>
#include <vm_address_space.h>
#include <wait_for_objects.h>


//#define TRACE_THREAD
#ifdef TRACE_THREAD
#	define TRACE(x) dprintf x
#else
#	define TRACE(x) ;
#endif


#define THREAD_MAX_MESSAGE_SIZE		65536

// used to pass messages between thread_exit and thread_exit2

struct thread_exit_args {
	struct thread	*thread;
	area_id			old_kernel_stack;
	uint32			death_stack;
	sem_id			death_sem;
	team_id			original_team_id;
};

struct thread_key {
	thread_id id;
};

// global
spinlock thread_spinlock = 0;

// thread list
static struct thread sIdleThreads[B_MAX_CPU_COUNT];
static hash_table *sThreadHash = NULL;
static thread_id sNextThreadID = 1;

// some arbitrary chosen limits - should probably depend on the available
// memory (the limit is not yet enforced)
static int32 sMaxThreads = 4096;
static int32 sUsedThreads = 0;

static sem_id sSnoozeSem = -1;

// death stacks - used temporarily as a thread cleans itself up
struct death_stack {
	area_id	area;
	addr_t	address;
	bool	in_use;
};
static struct death_stack *sDeathStacks;
static unsigned int sNumDeathStacks;
static unsigned int volatile sDeathStackBitmap;
static sem_id sDeathStackSem;
static spinlock sDeathStackLock = 0;

// The dead queue is used as a pool from which to retrieve and reuse previously
// allocated thread structs when creating a new thread. It should be gone once
// the slab allocator is in.
struct thread_queue dead_q;

static void thread_kthread_entry(void);
static void thread_kthread_exit(void);


/*!
	Inserts a thread into a team.
	You must hold the team lock when you call this function.
*/
static void
insert_thread_into_team(struct team *team, struct thread *thread)
{
	thread->team_next = team->thread_list;
	team->thread_list = thread;
	team->num_threads++;

	if (team->num_threads == 1) {
		// this was the first thread
		team->main_thread = thread;
	}
	thread->team = team;
}


/*!
	Removes a thread from a team.
	You must hold the team lock when you call this function.
*/
static void
remove_thread_from_team(struct team *team, struct thread *thread)
{
	struct thread *temp, *last = NULL;

	for (temp = team->thread_list; temp != NULL; temp = temp->team_next) {
		if (temp == thread) {
			if (last == NULL)
				team->thread_list = temp->team_next;
			else
				last->team_next = temp->team_next;

			team->num_threads--;
			break;
		}
		last = temp;
	}
}


static int
thread_struct_compare(void *_t, const void *_key)
{
	struct thread *thread = (struct thread*)_t;
	const struct thread_key *key = (const struct thread_key*)_key;

	if (thread->id == key->id)
		return 0;

	return 1;
}


static uint32
thread_struct_hash(void *_t, const void *_key, uint32 range)
{
	struct thread *thread = (struct thread*)_t;
	const struct thread_key *key = (const struct thread_key*)_key;

	if (thread != NULL)
		return thread->id % range;

	return (uint32)key->id % range;
}


static void
reset_signals(struct thread *thread)
{
	thread->sig_pending = 0;
	thread->sig_block_mask = 0;
	memset(thread->sig_action, 0, 32 * sizeof(struct sigaction));
	thread->signal_stack_base = 0;
	thread->signal_stack_size = 0;
	thread->signal_stack_enabled = false;
}


/*!
	Allocates and fills in thread structure (or reuses one from the
	dead queue).

	\param threadID The ID to be assigned to the new thread. If
		  \code < 0 \endcode a fresh one is allocated.
	\param thread initialize this thread struct if nonnull
*/

static struct thread *
create_thread_struct(struct thread *inthread, const char *name,
	thread_id threadID, struct cpu_ent *cpu)
{
	struct thread *thread;
	cpu_status state;
	char temp[64];

	if (inthread == NULL) {
		// try to recycle one from the dead queue first
		state = disable_interrupts();
		GRAB_THREAD_LOCK();
		thread = thread_dequeue(&dead_q);
		RELEASE_THREAD_LOCK();
		restore_interrupts(state);

		// if not, create a new one
		if (thread == NULL) {
			thread = (struct thread *)malloc(sizeof(struct thread));
			if (thread == NULL)
				return NULL;
		}
	} else {
		thread = inthread;
	}

	if (name != NULL)
		strlcpy(thread->name, name, B_OS_NAME_LENGTH);
	else
		strcpy(thread->name, "unnamed thread");

	thread->flags = 0;
	thread->id = threadID >= 0 ? threadID : allocate_thread_id();
	thread->team = NULL;
	thread->cpu = cpu;
	thread->sem.blocking = -1;
	thread->condition_variable_entry = NULL;
	thread->fault_handler = 0;
	thread->page_faults_allowed = 1;
	thread->kernel_stack_area = -1;
	thread->kernel_stack_base = 0;
	thread->user_stack_area = -1;
	thread->user_stack_base = 0;
	thread->user_local_storage = 0;
	thread->kernel_errno = 0;
	thread->team_next = NULL;
	thread->queue_next = NULL;
	thread->priority = thread->next_priority = -1;
	thread->args1 = NULL;  thread->args2 = NULL;
	thread->alarm.period = 0;
	reset_signals(thread);
	thread->in_kernel = true;
	thread->was_yielded = false;
	thread->user_time = 0;
	thread->kernel_time = 0;
	thread->last_time = 0;
	thread->exit.status = 0;
	thread->exit.reason = 0;
	thread->exit.signal = 0;
	list_init(&thread->exit.waiters);
	thread->select_infos = NULL;

	sprintf(temp, "thread_%ld_retcode_sem", thread->id);
	thread->exit.sem = create_sem(0, temp);
	if (thread->exit.sem < B_OK)
		goto err1;

	sprintf(temp, "%s send", thread->name);
	thread->msg.write_sem = create_sem(1, temp);
	if (thread->msg.write_sem < B_OK)
		goto err2;

	sprintf(temp, "%s receive", thread->name);
	thread->msg.read_sem = create_sem(0, temp);
	if (thread->msg.read_sem < B_OK)
		goto err3;

	if (arch_thread_init_thread_struct(thread) < B_OK)
		goto err4;

	return thread;

err4:
	delete_sem(thread->msg.read_sem);
err3:
	delete_sem(thread->msg.write_sem);
err2:
	delete_sem(thread->exit.sem);
err1:
	// ToDo: put them in the dead queue instead?
	if (inthread == NULL)
		free(thread);
	return NULL;
}


static void
delete_thread_struct(struct thread *thread)
{
	delete_sem(thread->exit.sem);
	delete_sem(thread->msg.write_sem);
	delete_sem(thread->msg.read_sem);

	// ToDo: put them in the dead queue instead?
	free(thread);
}


/*! This function gets run by a new thread before anything else */
static void
thread_kthread_entry(void)
{
	struct thread *thread = thread_get_current_thread();

	// simulates the thread spinlock release that would occur if the thread had been
	// rescheded from. The resched didn't happen because the thread is new.
	RELEASE_THREAD_LOCK();

	// start tracking time
	thread->last_time = system_time();

	enable_interrupts(); // this essentially simulates a return-from-interrupt
}


static void
thread_kthread_exit(void)
{
	struct thread *thread = thread_get_current_thread();

	thread->exit.reason = THREAD_RETURN_EXIT;
	thread_exit();
}


/*!
	Initializes the thread and jumps to its userspace entry point.
	This function is called at creation time of every user thread,
	but not for a team's main thread.
*/
static int
_create_user_thread_kentry(void)
{
	struct thread *thread = thread_get_current_thread();

	// a signal may have been delivered here
	thread_at_kernel_exit();

	// jump to the entry point in user space
	arch_thread_enter_userspace(thread, (addr_t)thread->entry,
		thread->args1, thread->args2);

	// only get here if the above call fails
	return 0;
}


/*! Initializes the thread and calls it kernel space entry point. */
static int
_create_kernel_thread_kentry(void)
{
	struct thread *thread = thread_get_current_thread();
	int (*func)(void *args) = (int (*)(void *))thread->entry;

	// call the entry function with the appropriate args
	return func(thread->args1);
}


/*!
	Creates a new thread in the team with the specified team ID.

	\param threadID The ID to be assigned to the new thread. If
		  \code < 0 \endcode a fresh one is allocated.
*/
static thread_id
create_thread(const char *name, team_id teamID, thread_entry_func entry,
	void *args1, void *args2, int32 priority, bool kernel, thread_id threadID)
{
	struct thread *thread, *currentThread;
	struct team *team;
	cpu_status state;
	char stack_name[B_OS_NAME_LENGTH];
	status_t status;
	bool abort = false;
	bool debugNewThread = false;

	TRACE(("create_thread(%s, id = %ld, %s)\n", name, threadID,
		kernel ? "kernel" : "user"));

	thread = create_thread_struct(NULL, name, threadID, NULL);
	if (thread == NULL)
		return B_NO_MEMORY;

	thread->priority = priority == -1 ? B_NORMAL_PRIORITY : priority;
	thread->next_priority = thread->priority;
	// ToDo: this could be dangerous in case someone calls resume_thread() on us
	thread->state = B_THREAD_SUSPENDED;
	thread->next_state = B_THREAD_SUSPENDED;

	// init debug structure
	clear_thread_debug_info(&thread->debug_info, false);

	snprintf(stack_name, B_OS_NAME_LENGTH, "%s_%ld_kstack", name, thread->id);
	thread->kernel_stack_area = create_area(stack_name,
		(void **)&thread->kernel_stack_base, B_ANY_KERNEL_ADDRESS,
		KERNEL_STACK_SIZE, B_FULL_LOCK,
		B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA | B_KERNEL_STACK_AREA);

	if (thread->kernel_stack_area < 0) {
		// we're not yet part of a team, so we can just bail out
		status = thread->kernel_stack_area;

		dprintf("create_thread: error creating kernel stack: %s!\n",
			strerror(status));

		delete_thread_struct(thread);
		return status;
	}

	thread->kernel_stack_top = thread->kernel_stack_base + KERNEL_STACK_SIZE;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	// If the new thread belongs to the same team as the current thread,
	// it may inherit some of the thread debug flags.
	currentThread = thread_get_current_thread();
	if (currentThread && currentThread->team->id == teamID) {
		// inherit all user flags...
		int32 debugFlags = currentThread->debug_info.flags
			& B_THREAD_DEBUG_USER_FLAG_MASK;

		// ... save the syscall tracing flags, unless explicitely specified
		if (!(debugFlags & B_THREAD_DEBUG_SYSCALL_TRACE_CHILD_THREADS)) {
			debugFlags &= ~(B_THREAD_DEBUG_PRE_SYSCALL
				| B_THREAD_DEBUG_POST_SYSCALL);
		}

		thread->debug_info.flags = debugFlags;

		// stop the new thread, if desired
		debugNewThread = debugFlags & B_THREAD_DEBUG_STOP_CHILD_THREADS;
	}

	// insert into global list
	hash_insert(sThreadHash, thread);
	sUsedThreads++;
	RELEASE_THREAD_LOCK();

	GRAB_TEAM_LOCK();
	// look at the team, make sure it's not being deleted
	team = team_get_team_struct_locked(teamID);
	if (team != NULL && team->state != TEAM_STATE_DEATH) {
		// Debug the new thread, if the parent thread required that (see above),
		// or the respective global team debug flag is set. But only, if a
		// debugger is installed for the team.
		debugNewThread |= (atomic_get(&team->debug_info.flags)
			& B_TEAM_DEBUG_STOP_NEW_THREADS);
		if (debugNewThread
			&& (atomic_get(&team->debug_info.flags)
				& B_TEAM_DEBUG_DEBUGGER_INSTALLED)) {
			thread->debug_info.flags |= B_THREAD_DEBUG_STOP;
		}

		insert_thread_into_team(team, thread);
	} else
		abort = true;

	RELEASE_TEAM_LOCK();
	if (abort) {
		GRAB_THREAD_LOCK();
		hash_remove(sThreadHash, thread);
		RELEASE_THREAD_LOCK();
	}
	restore_interrupts(state);
	if (abort) {
		delete_area(thread->kernel_stack_area);
		delete_thread_struct(thread);
		return B_BAD_TEAM_ID;
	}

	thread->args1 = args1;
	thread->args2 = args2;
	thread->entry = entry;
	status = thread->id;

	if (kernel) {
		// this sets up an initial kthread stack that runs the entry

		// Note: whatever function wants to set up a user stack later for this
		// thread must initialize the TLS for it
		arch_thread_init_kthread_stack(thread, &_create_kernel_thread_kentry,
			&thread_kthread_entry, &thread_kthread_exit);
	} else {
		// create user stack

		// the stack will be between USER_STACK_REGION and the main thread stack area
		// (the user stack of the main thread is created in team_create_team())
		thread->user_stack_base = USER_STACK_REGION;
		thread->user_stack_size = USER_STACK_SIZE;

		snprintf(stack_name, B_OS_NAME_LENGTH, "%s_%ld_stack", name, thread->id);
		thread->user_stack_area = create_area_etc(team, stack_name,
				(void **)&thread->user_stack_base, B_BASE_ADDRESS,
				thread->user_stack_size + TLS_SIZE, B_NO_LOCK,
				B_READ_AREA | B_WRITE_AREA | B_STACK_AREA);
		if (thread->user_stack_area < B_OK
			|| arch_thread_init_tls(thread) < B_OK) {
			// great, we have a fully running thread without a (usable) stack
			dprintf("create_thread: unable to create proper user stack!\n");
			status = thread->user_stack_area;
			kill_thread(thread->id);
		}

		user_debug_update_new_thread_flags(thread->id);

		// copy the user entry over to the args field in the thread struct
		// the function this will call will immediately switch the thread into
		// user space.
		arch_thread_init_kthread_stack(thread, &_create_user_thread_kentry,
			&thread_kthread_entry, &thread_kthread_exit);
	}

	return status;
}


/*!
	Finds a free death stack for us and allocates it.
	Must be called with interrupts enabled.
*/
static uint32
get_death_stack(void)
{
	cpu_status state;
	uint32 bit;
	int32 i;

	acquire_sem(sDeathStackSem);

	// grab the death stack and thread locks, find a free spot and release

	state = disable_interrupts();

	acquire_spinlock(&sDeathStackLock);
	GRAB_THREAD_LOCK();

	bit = sDeathStackBitmap;
	bit = (~bit) & ~((~bit) - 1);
	sDeathStackBitmap |= bit;

	RELEASE_THREAD_LOCK();
	release_spinlock(&sDeathStackLock);

	restore_interrupts(state);

	// sanity checks
	if (!bit)
		panic("get_death_stack: couldn't find free stack!\n");

	if (bit & (bit - 1))
		panic("get_death_stack: impossible bitmap result!\n");

	// bit to number
	for (i = -1; bit; i++) {
		bit >>= 1;
	}

	TRACE(("get_death_stack: returning %#lx\n", sDeathStacks[i].address));

	return (uint32)i;
}


/*!	Returns the thread's death stack to the pool.
	Interrupts must be disabled and the sDeathStackLock be held.
*/
static void
put_death_stack(uint32 index)
{
	TRACE(("put_death_stack...: passed %lu\n", index));

	if (index >= sNumDeathStacks)
		panic("put_death_stack: passed invalid stack index %ld\n", index);

	if (!(sDeathStackBitmap & (1 << index)))
		panic("put_death_stack: passed invalid stack index %ld\n", index);

	GRAB_THREAD_LOCK();
	sDeathStackBitmap &= ~(1 << index);
	RELEASE_THREAD_LOCK();

	release_sem_etc(sDeathStackSem, 1, B_DO_NOT_RESCHEDULE);
		// we must not hold the thread lock when releasing a semaphore
}


static void
thread_exit2(void *_args)
{
	struct thread_exit_args args;

	// copy the arguments over, since the source is probably on the kernel
	// stack we're about to delete
	memcpy(&args, _args, sizeof(struct thread_exit_args));

	// we can't let the interrupts disabled at this point
	enable_interrupts();

	TRACE(("thread_exit2, running on death stack %#lx\n", args.death_stack));

	// delete the old kernel stack area
	TRACE(("thread_exit2: deleting old kernel stack id %ld for thread %ld\n",
		args.old_kernel_stack, args.thread->id));

	delete_area(args.old_kernel_stack);

	// remove this thread from all of the global lists
	TRACE(("thread_exit2: removing thread %ld from global lists\n",
		args.thread->id));

	disable_interrupts();
	GRAB_TEAM_LOCK();

	remove_thread_from_team(team_get_kernel_team(), args.thread);

	RELEASE_TEAM_LOCK();
	enable_interrupts();
		// needed for the debugger notification below

	TRACE(("thread_exit2: done removing thread from lists\n"));

	if (args.death_sem >= 0)
		release_sem_etc(args.death_sem, 1, B_DO_NOT_RESCHEDULE);

	// notify the debugger
	if (args.original_team_id >= 0
		&& args.original_team_id != team_get_kernel_team_id()) {
		user_debug_thread_deleted(args.original_team_id, args.thread->id);
	}

	disable_interrupts();

	// Set the next state to be gone: this will cause the thread structure
	// to be returned to a ready pool upon reschedule.
	// Note, we need to have disabled interrupts at this point, or else
	// we could get rescheduled too early.
	args.thread->next_state = THREAD_STATE_FREE_ON_RESCHED;

	// return the death stack and reschedule one last time

	// Note that we need to hold sDeathStackLock until we've got the thread
	// lock. Otherwise someone else might grab our stack in the meantime.
	acquire_spinlock(&sDeathStackLock);
	put_death_stack(args.death_stack);

	GRAB_THREAD_LOCK();
	release_spinlock(&sDeathStackLock);

	scheduler_reschedule();
		// requires thread lock to be held

	// never get to here
	panic("thread_exit2: made it where it shouldn't have!\n");
}


/*!
	Fills the thread_info structure with information from the specified
	thread.
	The thread lock must be held when called.
*/
static void
fill_thread_info(struct thread *thread, thread_info *info, size_t size)
{
	info->thread = thread->id;
	info->team = thread->team->id;

	strlcpy(info->name, thread->name, B_OS_NAME_LENGTH);

	if (thread->state == B_THREAD_WAITING) {
		if (thread->sem.blocking == sSnoozeSem)
			info->state = B_THREAD_ASLEEP;
		else if (thread->sem.blocking == thread->msg.read_sem)
			info->state = B_THREAD_RECEIVING;
		else
			info->state = B_THREAD_WAITING;
	} else
		info->state = (thread_state)thread->state;

	info->priority = thread->priority;
	info->sem = thread->sem.blocking;
	info->user_time = thread->user_time;
	info->kernel_time = thread->kernel_time;
	info->stack_base = (void *)thread->user_stack_base;
	info->stack_end = (void *)(thread->user_stack_base
		+ thread->user_stack_size);
}


static status_t
send_data_etc(thread_id id, int32 code, const void *buffer,
	size_t bufferSize, int32 flags)
{
	struct thread *target;
	sem_id cachedSem;
	cpu_status state;
	status_t status;
	cbuf *data;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();
	target = thread_get_thread_struct_locked(id);
	if (!target) {
		RELEASE_THREAD_LOCK();
		restore_interrupts(state);
		return B_BAD_THREAD_ID;
	}
	cachedSem = target->msg.write_sem;
	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	if (bufferSize > THREAD_MAX_MESSAGE_SIZE)
		return B_NO_MEMORY;

	status = acquire_sem_etc(cachedSem, 1, flags, 0);
	if (status == B_INTERRUPTED) {
		// We got interrupted by a signal
		return status;
	}
	if (status != B_OK) {
		// Any other acquisition problems may be due to thread deletion
		return B_BAD_THREAD_ID;
	}

	if (bufferSize > 0) {
		data = cbuf_get_chain(bufferSize);
		if (data == NULL)
			return B_NO_MEMORY;
		status = cbuf_user_memcpy_to_chain(data, 0, buffer, bufferSize);
		if (status < B_OK) {
			cbuf_free_chain(data);
			return B_NO_MEMORY;
		}
	} else
		data = NULL;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	// The target thread could have been deleted at this point
	target = thread_get_thread_struct_locked(id);
	if (target == NULL) {
		RELEASE_THREAD_LOCK();
		restore_interrupts(state);
		cbuf_free_chain(data);
		return B_BAD_THREAD_ID;
	}

	// Save message informations
	target->msg.sender = thread_get_current_thread()->id;
	target->msg.code = code;
	target->msg.size = bufferSize;
	target->msg.buffer = data;
	cachedSem = target->msg.read_sem;

	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	release_sem(cachedSem);
	return B_OK;
}


static int32
receive_data_etc(thread_id *_sender, void *buffer, size_t bufferSize,
	int32 flags)
{
	struct thread *thread = thread_get_current_thread();
	status_t status;
	size_t size;
	int32 code;

	status = acquire_sem_etc(thread->msg.read_sem, 1, flags, 0);
	if (status < B_OK) {
		// Actually, we're not supposed to return error codes
		// but since the only reason this can fail is that we
		// were killed, it's probably okay to do so (but also
		// meaningless).
		return status;
	}

	if (buffer != NULL && bufferSize != 0) {
		size = min_c(bufferSize, thread->msg.size);
		status = cbuf_user_memcpy_from_chain(buffer, thread->msg.buffer,
			0, size);
		if (status < B_OK) {
			cbuf_free_chain(thread->msg.buffer);
			release_sem(thread->msg.write_sem);
			return status;
		}
	}

	*_sender = thread->msg.sender;
	code = thread->msg.code;

	cbuf_free_chain(thread->msg.buffer);
	release_sem(thread->msg.write_sem);

	return code;
}


//	#pragma mark - debugger calls


static int
make_thread_unreal(int argc, char **argv)
{
	struct thread *thread;
	struct hash_iterator i;
	int32 id = -1;

	if (argc > 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	if (argc > 1)
		id = strtoul(argv[1], NULL, 0);

	hash_open(sThreadHash, &i);

	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		if (id != -1 && thread->id != id)
			continue;

		if (thread->priority > B_DISPLAY_PRIORITY) {
			thread->priority = thread->next_priority = B_NORMAL_PRIORITY;
			kprintf("thread %ld made unreal\n", thread->id);
		}
	}

	hash_close(sThreadHash, &i, false);
	return 0;
}


static int
set_thread_prio(int argc, char **argv)
{
	struct thread *thread;
	struct hash_iterator i;
	int32 id;
	int32 prio;

	if (argc > 3 || argc < 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	prio = strtoul(argv[1], NULL, 0);
	if (prio > B_MAX_PRIORITY)
		prio = B_MAX_PRIORITY;
	if (prio < B_MIN_PRIORITY)
		prio = B_MIN_PRIORITY;

	if (argc > 2)
		id = strtoul(argv[2], NULL, 0);
	else
		id = thread_get_current_thread()->id;

	hash_open(sThreadHash, &i);

	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		if (thread->id != id)
			continue;
		thread->priority = thread->next_priority = prio;
		kprintf("thread %ld set to priority %ld\n", id, prio);
		break;
	}
	if (!thread)
		kprintf("thread %ld (%#lx) not found\n", id, id);

	hash_close(sThreadHash, &i, false);
	return 0;
}


static int
make_thread_suspended(int argc, char **argv)
{
	struct thread *thread;
	struct hash_iterator i;
	int32 id;

	if (argc > 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	if (argc == 1)
		id = thread_get_current_thread()->id;
	else
		id = strtoul(argv[1], NULL, 0);

	hash_open(sThreadHash, &i);

	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		if (thread->id != id)
			continue;

		thread->next_state = B_THREAD_SUSPENDED;
		kprintf("thread %ld suspended\n", id);
		break;
	}
	if (!thread)
		kprintf("thread %ld (%#lx) not found\n", id, id);

	hash_close(sThreadHash, &i, false);
	return 0;
}


static int
make_thread_resumed(int argc, char **argv)
{
	struct thread *thread;
	struct hash_iterator i;
	int32 id;

	if (argc != 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	// force user to enter a thread id, as using
	// the current thread is usually not intended
	id = strtoul(argv[1], NULL, 0);

	hash_open(sThreadHash, &i);

	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		if (thread->id != id)
			continue;

		if (thread->state == B_THREAD_SUSPENDED) {
			scheduler_enqueue_in_run_queue(thread);
			kprintf("thread %ld resumed\n", thread->id);
		}
		break;
	}
	if (!thread)
		kprintf("thread %ld (%#lx) not found\n", id, id);

	hash_close(sThreadHash, &i, false);
	return 0;
}


static int
drop_into_debugger(int argc, char **argv)
{
	status_t err;
	int32 id;

	if (argc > 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	if (argc == 1)
		id = thread_get_current_thread()->id;
	else
		id = strtoul(argv[1], NULL, 0);

	err = _user_debug_thread(id);
	if (err)
		kprintf("drop failed\n");
	else
		kprintf("thread %ld dropped into user debugger\n", id);

	return 0;
}


static const char *
state_to_text(struct thread *thread, int32 state)
{
	switch (state) {
		case B_THREAD_READY:
			return "ready";

		case B_THREAD_RUNNING:
			return "running";

		case B_THREAD_WAITING:
			if (thread->sem.blocking == sSnoozeSem)
				return "zzz";
			if (thread->sem.blocking == thread->msg.read_sem)
				return "receive";

			return "waiting";

		case B_THREAD_SUSPENDED:
			return "suspended";

		case THREAD_STATE_FREE_ON_RESCHED:
			return "death";

		default:
			return "UNKNOWN";
	}
}


static void
_dump_thread_info(struct thread *thread)
{
	struct death_entry *death = NULL;

	kprintf("THREAD: %p\n", thread);
	kprintf("id:                 %ld (%#lx)\n", thread->id, thread->id);
	kprintf("name:               \"%s\"\n", thread->name);
	kprintf("all_next:           %p\nteam_next:          %p\nq_next:             %p\n",
		thread->all_next, thread->team_next, thread->queue_next);
	kprintf("priority:           %ld (next %ld)\n", thread->priority, thread->next_priority);
	kprintf("state:              %s\n", state_to_text(thread, thread->state));
	kprintf("next_state:         %s\n", state_to_text(thread, thread->next_state));
	kprintf("cpu:                %p ", thread->cpu);
	if (thread->cpu)
		kprintf("(%d)\n", thread->cpu->cpu_num);
	else
		kprintf("\n");
	kprintf("sig_pending:        %#lx (blocked: %#lx)\n", thread->sig_pending,
		thread->sig_block_mask);
	kprintf("in_kernel:          %d\n", thread->in_kernel);
	kprintf("  sem.blocking:     %ld\n", thread->sem.blocking);
	kprintf("  sem.count:        %ld\n", thread->sem.count);
	kprintf("  sem.acquire_status: %#lx\n", thread->sem.acquire_status);
	kprintf("  sem.flags:        %#lx\n", thread->sem.flags);

	kprintf("condition variables:");
	PrivateConditionVariableEntry* entry = thread->condition_variable_entry;
	while (entry != NULL) {
		kprintf(" %p", entry->Variable());
		entry = entry->ThreadNext();
	}
	kprintf("\n");

	kprintf("fault_handler:      %p\n", (void *)thread->fault_handler);
	kprintf("args:               %p %p\n", thread->args1, thread->args2);
	kprintf("entry:              %p\n", (void *)thread->entry);
	kprintf("team:               %p, \"%s\"\n", thread->team, thread->team->name);
	kprintf("  exit.sem:         %ld\n", thread->exit.sem);
	kprintf("  exit.status:      %#lx (%s)\n", thread->exit.status, strerror(thread->exit.status));
	kprintf("  exit.reason:      %#x\n", thread->exit.reason);
	kprintf("  exit.signal:      %#x\n", thread->exit.signal);
	kprintf("  exit.waiters:\n");
	while ((death = (struct death_entry*)list_get_next_item(
			&thread->exit.waiters, death)) != NULL) {
		kprintf("\t%p (group %ld, thread %ld)\n", death, death->group_id, death->thread);
	}

	kprintf("kernel_stack_area:  %ld\n", thread->kernel_stack_area);
	kprintf("kernel_stack_base:  %p\n", (void *)thread->kernel_stack_base);
	kprintf("user_stack_area:    %ld\n", thread->user_stack_area);
	kprintf("user_stack_base:    %p\n", (void *)thread->user_stack_base);
	kprintf("user_local_storage: %p\n", (void *)thread->user_local_storage);
	kprintf("kernel_errno:       %#x (%s)\n", thread->kernel_errno,
		strerror(thread->kernel_errno));
	kprintf("kernel_time:        %Ld\n", thread->kernel_time);
	kprintf("user_time:          %Ld\n", thread->user_time);
	kprintf("flags:              0x%lx\n", thread->flags);
	kprintf("architecture dependant section:\n");
	arch_thread_dump_info(&thread->arch_info);
}


static int
dump_thread_info(int argc, char **argv)
{
	const char *name = NULL;
	struct thread *thread;
	int32 id = -1;
	struct hash_iterator i;
	bool found = false;

	if (argc > 2) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	if (argc == 1) {
		_dump_thread_info(thread_get_current_thread());
		return 0;
	} else {
		name = argv[1];
		id = strtoul(argv[1], NULL, 0);

		if (IS_KERNEL_ADDRESS(id)) {
			// semi-hack
			_dump_thread_info((struct thread *)id);
			return 0;
		}
	}

	// walk through the thread list, trying to match name or id
	hash_open(sThreadHash, &i);
	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		if ((name != NULL && !strcmp(name, thread->name)) || thread->id == id) {
			_dump_thread_info(thread);
			found = true;
			break;
		}
	}
	hash_close(sThreadHash, &i, false);

	if (!found)
		kprintf("thread \"%s\" (%ld) doesn't exist!\n", argv[1], id);
	return 0;
}


static int
dump_thread_list(int argc, char **argv)
{
	struct thread *thread;
	struct hash_iterator i;
	bool realTimeOnly = false;
	bool calling = false;
	const char *callSymbol = NULL;
	addr_t callStart = 0;
	addr_t callEnd = 0;
	int32 requiredState = 0;
	team_id team = -1;
	sem_id sem = -1;

	if (!strcmp(argv[0], "realtime"))
		realTimeOnly = true;
	else if (!strcmp(argv[0], "ready"))
		requiredState = B_THREAD_READY;
	else if (!strcmp(argv[0], "running"))
		requiredState = B_THREAD_RUNNING;
	else if (!strcmp(argv[0], "waiting")) {
		requiredState = B_THREAD_WAITING;

		if (argc > 1) {
			sem = strtoul(argv[1], NULL, 0);
			if (sem == 0)
				kprintf("ignoring invalid semaphore argument.\n");
		}
	} else if (!strcmp(argv[0], "calling")) {
		if (argc < 2) {
			kprintf("Need to give a symbol name or start and end arguments.\n");
			return 0;
		} else if (argc == 3) {
			callStart = parse_expression(argv[1]);
			callEnd = parse_expression(argv[2]);
		} else
			callSymbol = argv[1];

		calling = true;
	} else if (argc > 1) {
		team = strtoul(argv[1], NULL, 0);
		if (team == 0)
			kprintf("ignoring invalid team argument.\n");
	}

	kprintf("thread         id  state        sem/cv cpu pri  stack      team  "
		"name\n");

	hash_open(sThreadHash, &i);
	while ((thread = (struct thread*)hash_next(sThreadHash, &i)) != NULL) {
		// filter out threads not matching the search criteria
		if ((requiredState && thread->state != requiredState)
			|| (calling && !arch_debug_contains_call(thread, callSymbol,
					callStart, callEnd))
			|| (sem > 0 && thread->sem.blocking != sem)
			|| (team > 0 && thread->team->id != team)
			|| (realTimeOnly && thread->priority < B_REAL_TIME_DISPLAY_PRIORITY))
			continue;

		kprintf("%p %6ld  %-9s", thread, thread->id, state_to_text(thread,
			thread->state));

		// does it block on a semaphore or a condition variable?
		if (thread->state == B_THREAD_WAITING) {
			if (thread->condition_variable_entry)
				kprintf("%p  ", thread->condition_variable_entry->Variable());
			else
				kprintf("%10ld  ", thread->sem.blocking);
		} else
			kprintf("      -     ");

		// on which CPU does it run?
		if (thread->cpu)
			kprintf("%2d", thread->cpu->cpu_num);
		else
			kprintf(" -");

		kprintf("%4ld  %p%5ld  %s\n", thread->priority,
			(void *)thread->kernel_stack_base, thread->team->id,
			thread->name != NULL ? thread->name : "<NULL>");
	}
	hash_close(sThreadHash, &i, false);
	return 0;
}


//	#pragma mark - private kernel API


void
thread_exit(void)
{
	cpu_status state;
	struct thread *thread = thread_get_current_thread();
	struct team *team = thread->team;
	thread_id parentID = -1;
	bool deleteTeam = false;
	sem_id cachedDeathSem = -1;
	status_t status;
	struct thread_debug_info debugInfo;
	team_id teamID = team->id;

	TRACE(("thread %ld exiting %s w/return code %#lx\n", thread->id,
		thread->exit.reason == THREAD_RETURN_INTERRUPTED
			? "due to signal" : "normally", thread->exit.status));

	if (!are_interrupts_enabled())
		panic("thread_exit() called with interrupts disabled!\n");

	// boost our priority to get this over with
	thread->priority = thread->next_priority = B_URGENT_DISPLAY_PRIORITY;

	// Cancel previously installed alarm timer, if any
	cancel_timer(&thread->alarm);

	// delete the user stack area first, we won't need it anymore
	if (team->address_space != NULL && thread->user_stack_area >= 0) {
		area_id area = thread->user_stack_area;
		thread->user_stack_area = -1;
		delete_area_etc(team, area);
	}

	struct job_control_entry *death = NULL;
	struct death_entry* threadDeathEntry = NULL;

	if (team != team_get_kernel_team()) {
		if (team->main_thread == thread) {
			// this was the main thread in this team, so we will delete that as well
			deleteTeam = true;
		} else
			threadDeathEntry = (death_entry*)malloc(sizeof(death_entry));

		// remove this thread from the current team and add it to the kernel
		// put the thread into the kernel team until it dies
		state = disable_interrupts();
		GRAB_TEAM_LOCK();
		GRAB_THREAD_LOCK();
			// removing the thread and putting its death entry to the parent
			// team needs to be an atomic operation

		// remember how long this thread lasted
		team->dead_threads_kernel_time += thread->kernel_time;
		team->dead_threads_user_time += thread->user_time;

		remove_thread_from_team(team, thread);
		insert_thread_into_team(team_get_kernel_team(), thread);

		cachedDeathSem = team->death_sem;

		if (deleteTeam) {
			struct team *parent = team->parent;

			// remember who our parent was so we can send a signal
			parentID = parent->id;

			// Set the team job control state to "dead" and detach the job
			// control entry from our team struct.
			team_set_job_control_state(team, JOB_CONTROL_STATE_DEAD, 0, true);
			death = team->job_control_entry;
			team->job_control_entry = NULL;

			if (death != NULL) {
				death->InitDeadState();

				// team_set_job_control_state() already moved our entry
				// into the parent's list. We just check the soft limit of
				// death entries.
				if (parent->dead_children->count > MAX_DEAD_CHILDREN) {
					death = parent->dead_children->entries.RemoveHead();
					parent->dead_children->count--;
				} else
					death = NULL;

				RELEASE_THREAD_LOCK();
			} else
				RELEASE_THREAD_LOCK();

			team_remove_team(team);

			send_signal_etc(parentID, SIGCHLD,
				SIGNAL_FLAG_TEAMS_LOCKED | B_DO_NOT_RESCHEDULE);
		} else {
			// The thread is not the main thread. We store a thread death
			// entry for it, unless someone is already waiting it.
			if (threadDeathEntry != NULL
				&& list_is_empty(&thread->exit.waiters)) {
				threadDeathEntry->thread = thread->id;
				threadDeathEntry->status = thread->exit.status;
				threadDeathEntry->reason = thread->exit.reason;
				threadDeathEntry->signal = thread->exit.signal;

				// add entry -- remove and old one, if we hit the limit
				list_add_item(&team->dead_threads, threadDeathEntry);
				team->dead_threads_count++;
				threadDeathEntry = NULL;

				if (team->dead_threads_count > MAX_DEAD_THREADS) {
					threadDeathEntry = (death_entry*)list_remove_head_item(
						&team->dead_threads);
					team->dead_threads_count--;
				}
			}

			RELEASE_THREAD_LOCK();
		}

		RELEASE_TEAM_LOCK();

		// swap address spaces, to make sure we're running on the kernel's pgdir
		vm_swap_address_space(vm_kernel_address_space());
		restore_interrupts(state);

		TRACE(("thread_exit: thread %ld now a kernel thread!\n", thread->id));
	}

	if (threadDeathEntry != NULL)
		free(threadDeathEntry);

	// delete the team if we're its main thread
	if (deleteTeam) {
		team_delete_team(team);

		// we need to delete any death entry that made it to here
		if (death != NULL)
			delete death;

		cachedDeathSem = -1;
	}

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	// remove thread from hash, so it's no longer accessible
	hash_remove(sThreadHash, thread);
	sUsedThreads--;

	// Stop debugging for this thread
	debugInfo = thread->debug_info;
	clear_thread_debug_info(&thread->debug_info, true);

	// Remove the select infos. We notify them a little later.
	select_info* selectInfos = thread->select_infos;
	thread->select_infos = NULL;

	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	destroy_thread_debug_info(&debugInfo);

	// notify select infos
	select_info* info = selectInfos;
	while (info != NULL) {
		select_sync* sync = info->sync;

		notify_select_events(info, B_EVENT_INVALID);
		info = info->next;
		put_select_sync(sync);
	}

	// shutdown the thread messaging

	status = acquire_sem_etc(thread->msg.write_sem, 1, B_RELATIVE_TIMEOUT, 0);
	if (status == B_WOULD_BLOCK) {
		// there is data waiting for us, so let us eat it
		thread_id sender;

		delete_sem(thread->msg.write_sem);
			// first, let's remove all possibly waiting writers
		receive_data_etc(&sender, NULL, 0, B_RELATIVE_TIMEOUT);
	} else {
		// we probably own the semaphore here, and we're the last to do so
		delete_sem(thread->msg.write_sem);
	}
	// now we can safely remove the msg.read_sem
	delete_sem(thread->msg.read_sem);

	// fill all death entries and delete the sem that others will use to wait on us
	{
		sem_id cachedExitSem = thread->exit.sem;
		cpu_status state;

		state = disable_interrupts();
		GRAB_THREAD_LOCK();

		// make sure no one will grab this semaphore again
		thread->exit.sem = -1;

		// fill all death entries
		death_entry* entry = NULL;
		while ((entry = (struct death_entry*)list_get_next_item(
				&thread->exit.waiters, entry)) != NULL) {
			entry->status = thread->exit.status;
			entry->reason = thread->exit.reason;
			entry->signal = thread->exit.signal;
		}

		RELEASE_THREAD_LOCK();
		restore_interrupts(state);

		delete_sem(cachedExitSem);
	}

	{
		struct thread_exit_args args;

		args.thread = thread;
		args.old_kernel_stack = thread->kernel_stack_area;
		args.death_stack = get_death_stack();
		args.death_sem = cachedDeathSem;
		args.original_team_id = teamID;


		disable_interrupts();

		// set the new kernel stack officially to the death stack, it won't be
		// switched until the next function is called. This must be done now
		// before a context switch, or we'll stay on the old stack
		thread->kernel_stack_area = sDeathStacks[args.death_stack].area;
		thread->kernel_stack_base = sDeathStacks[args.death_stack].address;

		// we will continue in thread_exit2(), on the new stack
		arch_thread_switch_kstack_and_call(thread, thread->kernel_stack_base
			 + KERNEL_STACK_SIZE, thread_exit2, &args);
	}

	panic("never can get here\n");
}


struct thread *
thread_get_thread_struct(thread_id id)
{
	struct thread *thread;
	cpu_status state;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	thread = thread_get_thread_struct_locked(id);

	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	return thread;
}


struct thread *
thread_get_thread_struct_locked(thread_id id)
{
	struct thread_key key;

	key.id = id;

	return (struct thread*)hash_lookup(sThreadHash, &key);
}


/*!
	Called in the interrupt handler code when a thread enters
	the kernel for any reason.
	Only tracks time for now.
	Interrupts are disabled.
*/
void
thread_at_kernel_entry(bigtime_t now)
{
	struct thread *thread = thread_get_current_thread();

	TRACE(("thread_at_kernel_entry: entry thread %ld\n", thread->id));

	// track user time
	thread->user_time += now - thread->last_time;
	thread->last_time = now;

	thread->in_kernel = true;
}


/*!
	Called whenever a thread exits kernel space to user space.
	Tracks time, handles signals, ...
*/
void
thread_at_kernel_exit(void)
{
	struct thread *thread = thread_get_current_thread();

	TRACE(("thread_at_kernel_exit: exit thread %ld\n", thread->id));

	while (handle_signals(thread)) {
		InterruptsSpinLocker _(thread_spinlock);
		scheduler_reschedule();
	}

	cpu_status state = disable_interrupts();

	thread->in_kernel = false;

	// track kernel time
	bigtime_t now = system_time();
	thread->kernel_time += now - thread->last_time;
	thread->last_time = now;

	restore_interrupts(state);
}


/*!	The quick version of thread_kernel_exit(), in case no signals are pending
	and no debugging shall be done.
	Interrupts are disabled in this case.
*/
void
thread_at_kernel_exit_no_signals(void)
{
	struct thread *thread = thread_get_current_thread();

	TRACE(("thread_at_kernel_exit_no_signals: exit thread %ld\n", thread->id));

	thread->in_kernel = false;

	// track kernel time
	bigtime_t now = system_time();
	thread->kernel_time += now - thread->last_time;
	thread->last_time = now;
}


void
thread_reset_for_exec(void)
{
	struct thread *thread = thread_get_current_thread();

	cancel_timer(&thread->alarm);
	reset_signals(thread);
}


/*! Insert a thread to the tail of a queue */
void
thread_enqueue(struct thread *thread, struct thread_queue *queue)
{
	thread->queue_next = NULL;
	if (queue->head == NULL) {
		queue->head = thread;
		queue->tail = thread;
	} else {
		queue->tail->queue_next = thread;
		queue->tail = thread;
	}
}


struct thread *
thread_lookat_queue(struct thread_queue *queue)
{
	return queue->head;
}


struct thread *
thread_dequeue(struct thread_queue *queue)
{
	struct thread *thread = queue->head;

	if (thread != NULL) {
		queue->head = thread->queue_next;
		if (queue->tail == thread)
			queue->tail = NULL;
	}
	return thread;
}


struct thread *
thread_dequeue_id(struct thread_queue *q, thread_id id)
{
	struct thread *thread;
	struct thread *last = NULL;

	thread = q->head;
	while (thread != NULL) {
		if (thread->id == id) {
			if (last == NULL)
				q->head = thread->queue_next;
			else
				last->queue_next = thread->queue_next;

			if (q->tail == thread)
				q->tail = last;
			break;
		}
		last = thread;
		thread = thread->queue_next;
	}
	return thread;
}


thread_id
allocate_thread_id(void)
{
	return atomic_add(&sNextThreadID, 1);
}


thread_id
peek_next_thread_id(void)
{
	return atomic_get(&sNextThreadID);
}


/*!	Yield the CPU to other threads.
	If \a force is \c true, the thread will almost guaranteedly be unscheduled.
	If \c false, it will continue to run, if there's no other thread in ready
	state, and if it has a higher priority than the other ready threads, it
	still has a good chance to continue.
*/
void
thread_yield(bool force)
{
	if (force) {
		// snooze for roughly 3 thread quantums
		snooze_etc(9000, B_SYSTEM_TIMEBASE, B_RELATIVE_TIMEOUT | B_CAN_INTERRUPT);
#if 0
		cpu_status state;

		struct thread *thread = thread_get_current_thread();
		if (thread == NULL)
			return;

		state = disable_interrupts();
		GRAB_THREAD_LOCK();

		// mark the thread as yielded, so it will not be scheduled next
		//thread->was_yielded = true;
		thread->next_priority = B_LOWEST_ACTIVE_PRIORITY;
		scheduler_reschedule();

		RELEASE_THREAD_LOCK();
		restore_interrupts(state);
#endif
	} else {
		struct thread *thread = thread_get_current_thread();
		if (thread == NULL)
			return;

		// Don't force the thread off the CPU, just reschedule.
		InterruptsSpinLocker _(thread_spinlock);
		scheduler_reschedule();
	}
}


/*!
	Kernel private thread creation function.

	\param threadID The ID to be assigned to the new thread. If
		  \code < 0 \endcode a fresh one is allocated.
*/
thread_id
spawn_kernel_thread_etc(thread_func function, const char *name, int32 priority,
	void *arg, team_id team, thread_id threadID)
{
	return create_thread(name, team, (thread_entry_func)function, arg, NULL,
		priority, true, threadID);
}


status_t
wait_for_thread_etc(thread_id id, uint32 flags, bigtime_t timeout,
	status_t *_returnCode)
{
	sem_id exitSem = B_BAD_THREAD_ID;
	struct death_entry death;
	job_control_entry* freeDeath = NULL;
	struct thread *thread;
	cpu_status state;
	status_t status = B_OK;

	if (id < B_OK)
		return B_BAD_THREAD_ID;

	// we need to resume the thread we're waiting for first

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	thread = thread_get_thread_struct_locked(id);
	if (thread != NULL) {
		// remember the semaphore we have to wait on and place our death entry
		exitSem = thread->exit.sem;
		list_add_link_to_head(&thread->exit.waiters, &death);
	}

	death_entry* threadDeathEntry = NULL;

	RELEASE_THREAD_LOCK();

	if (thread == NULL) {
		// we couldn't find this thread - maybe it's already gone, and we'll
		// find its death entry in our team
		GRAB_TEAM_LOCK();

		struct team* team = thread_get_current_thread()->team;

		// check the child death entries first (i.e. main threads of child
		// teams)
		bool deleteEntry;
		freeDeath = team_get_death_entry(team, id, &deleteEntry);
		if (freeDeath != NULL) {
			death.status = freeDeath->status;
			if (!deleteEntry)
				freeDeath = NULL;
		} else {
			// check the thread death entries of the team (non-main threads)
			while ((threadDeathEntry = (death_entry*)list_get_next_item(
					&team->dead_threads, threadDeathEntry)) != NULL) {
				if (threadDeathEntry->thread == id) {
					list_remove_item(&team->dead_threads, threadDeathEntry);
					team->dead_threads_count--;
					death.status = threadDeathEntry->status;
					break;
				}
			}

			if (threadDeathEntry == NULL)
				status = B_BAD_THREAD_ID;
		}

		RELEASE_TEAM_LOCK();
	}

	restore_interrupts(state);

	if (thread == NULL && status == B_OK) {
		// we found the thread's death entry in our team
		if (_returnCode)
			*_returnCode = death.status;

		delete freeDeath;
		free(threadDeathEntry);
		return B_OK;
	}

	// we need to wait for the death of the thread

	if (exitSem < B_OK)
		return B_BAD_THREAD_ID;

	resume_thread(id);
		// make sure we don't wait forever on a suspended thread

	status = acquire_sem_etc(exitSem, 1, flags, timeout);

	if (status == B_OK) {
		// this should never happen as the thread deletes the semaphore on exit
		panic("could acquire exit_sem for thread %ld\n", id);
	} else if (status == B_BAD_SEM_ID) {
		// this is the way the thread normally exits
		status = B_OK;

		if (_returnCode)
			*_returnCode = death.status;
	} else {
		// We were probably interrupted; we need to remove our death entry now.
		state = disable_interrupts();
		GRAB_THREAD_LOCK();

		thread = thread_get_thread_struct_locked(id);
		if (thread != NULL)
			list_remove_link(&death);

		RELEASE_THREAD_LOCK();
		restore_interrupts(state);

		// If the thread is already gone, we need to wait for its exit semaphore
		// to make sure our death entry stays valid - it won't take long
		if (thread == NULL)
			acquire_sem(exitSem);
	}

	return status;
}


status_t
select_thread(int32 id, struct select_info* info, bool kernel)
{
	InterruptsSpinLocker locker(thread_spinlock);

	// get thread
	struct thread* thread = thread_get_thread_struct_locked(id);
	if (thread == NULL)
		return B_BAD_THREAD_ID;

	// We support only B_EVENT_INVALID at the moment.
	info->selected_events &= B_EVENT_INVALID;

	// add info to list
	if (info->selected_events != 0) {
		info->next = thread->select_infos;
		thread->select_infos = info;

		// we need a sync reference
		atomic_add(&info->sync->ref_count, 1);
	}

	return B_OK;
}


status_t
deselect_thread(int32 id, struct select_info* info, bool kernel)
{
	InterruptsSpinLocker locker(thread_spinlock);

	// get thread
	struct thread* thread = thread_get_thread_struct_locked(id);
	if (thread == NULL)
		return B_BAD_THREAD_ID;

	// remove info from list
	select_info** infoLocation = &thread->select_infos;
	while (*infoLocation != NULL && *infoLocation != info)
		infoLocation = &(*infoLocation)->next;

	if (*infoLocation != info)
		return B_OK;

	*infoLocation = info->next;

	locker.Unlock();

	// surrender sync reference
	put_select_sync(info->sync);

	return B_OK;
}


int32
thread_max_threads(void)
{
	return sMaxThreads;
}


int32
thread_used_threads(void)
{
	return sUsedThreads;
}


status_t
thread_init(kernel_args *args)
{
	uint32 i;

	TRACE(("thread_init: entry\n"));

	// create the thread hash table
	sThreadHash = hash_init(15, offsetof(struct thread, all_next),
		&thread_struct_compare, &thread_struct_hash);

	// zero out the dead thread structure q
	memset(&dead_q, 0, sizeof(dead_q));

	// allocate snooze sem
	sSnoozeSem = create_sem(0, "snooze sem");
	if (sSnoozeSem < 0) {
		panic("error creating snooze sem\n");
		return sSnoozeSem;
	}

	if (arch_thread_init(args) < B_OK)
		panic("arch_thread_init() failed!\n");

	// skip all thread IDs including B_SYSTEM_TEAM, which is reserved
	sNextThreadID = B_SYSTEM_TEAM + 1;

	// create an idle thread for each cpu

	for (i = 0; i < args->num_cpus; i++) {
		struct thread *thread;
		area_info info;
		char name[64];

		sprintf(name, "idle thread %lu", i + 1);
		thread = create_thread_struct(&sIdleThreads[i], name,
			i == 0 ? team_get_kernel_team_id() : -1, &gCPU[i]);
		if (thread == NULL) {
			panic("error creating idle thread struct\n");
			return B_NO_MEMORY;
		}

		thread->team = team_get_kernel_team();
		thread->priority = thread->next_priority = B_IDLE_PRIORITY;
		thread->state = B_THREAD_RUNNING;
		thread->next_state = B_THREAD_READY;
		sprintf(name, "idle thread %lu kstack", i + 1);
		thread->kernel_stack_area = find_area(name);
		thread->entry = NULL;

		if (get_area_info(thread->kernel_stack_area, &info) != B_OK)
			panic("error finding idle kstack area\n");

		thread->kernel_stack_base = (addr_t)info.address;

		hash_insert(sThreadHash, thread);
		insert_thread_into_team(thread->team, thread);
	}
	sUsedThreads = args->num_cpus;

	// create a set of death stacks

	sNumDeathStacks = smp_get_num_cpus();
	if (sNumDeathStacks > 8 * sizeof(sDeathStackBitmap)) {
		// clamp values for really beefy machines
		sNumDeathStacks = 8 * sizeof(sDeathStackBitmap);
	}
	sDeathStackBitmap = 0;
	sDeathStacks = (struct death_stack *)malloc(sNumDeathStacks
		* sizeof(struct death_stack));
	if (sDeathStacks == NULL) {
		panic("error creating death stacks\n");
		return B_NO_MEMORY;
	}
	{
		char temp[64];

		for (i = 0; i < sNumDeathStacks; i++) {
			sprintf(temp, "death stack %lu", i);
			sDeathStacks[i].area = create_area(temp,
				(void **)&sDeathStacks[i].address, B_ANY_KERNEL_ADDRESS,
				KERNEL_STACK_SIZE, B_FULL_LOCK,
				B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA | B_KERNEL_STACK_AREA);
			if (sDeathStacks[i].area < 0) {
				panic("error creating death stacks\n");
				return sDeathStacks[i].area;
			}
			sDeathStacks[i].in_use = false;
		}
	}
	sDeathStackSem = create_sem(sNumDeathStacks, "death stack availability");

	// set up some debugger commands
	add_debugger_command_etc("threads", &dump_thread_list, "List all threads",
		"[ <team> ]\n"
		"Prints a list of all existing threads, or, if a team ID is given,\n"
		"all threads of the specified team.\n"
		"  <team>  - The ID of the team whose threads shall be listed.\n", 0);
	add_debugger_command_etc("ready", &dump_thread_list,
		"List all ready threads",
		"\n"
		"Prints a list of all threads in ready state.\n", 0);
	add_debugger_command_etc("running", &dump_thread_list,
		"List all running threads",
		"\n"
		"Prints a list of all threads in running state.\n", 0);
	add_debugger_command_etc("waiting", &dump_thread_list,
		"List all waiting threads (optionally for a specific semaphore)",
		"[ <sem> ]\n"
		"Prints a list of all threads in waiting state. If a semaphore is\n"
		"specified, only the threads waiting on that semaphore are listed.\n"
		"  <sem>  - ID of the semaphore.\n", 0);
	add_debugger_command_etc("realtime", &dump_thread_list,
		"List all realtime threads",
		"\n"
		"Prints a list of all threads with realtime priority.\n", 0);
	add_debugger_command_etc("thread", &dump_thread_info,
		"Dump info about a particular thread",
		"[ <id> | <address> | <name> ]\n"
		"Prints information about the specified thread. If no argument is\n"
		"given the current thread is selected.\n"
		"  <id>       - The ID of the thread.\n"
		"  <address>  - The address of the thread structure.\n"
		"  <name>     - The thread's name.\n", 0);
	add_debugger_command_etc("calling", &dump_thread_list,
		"Show all threads that have a specific address in their call chain",
		"{ <symbol-pattern> | <start> <end> }\n", 0);
	add_debugger_command_etc("unreal", &make_thread_unreal,
		"Set realtime priority threads to normal priority",
		"[ <id> ]\n"
		"Sets the priority of all realtime threads or, if given, the one\n"
		"with the specified ID to \"normal\" priority.\n"
		"  <id>  - The ID of the thread.\n", 0);
	add_debugger_command_etc("suspend", &make_thread_suspended,
		"Suspend a thread",
		"[ <id> ]\n"
		"Suspends the thread with the given ID. If no ID argument is given\n"
		"the current thread is selected.\n"
		"  <id>  - The ID of the thread.\n", 0);
	add_debugger_command_etc("resume", &make_thread_resumed, "Resume a thread",
		"<id>\n"
		"Resumes the specified thread, if it is currently suspended.\n"
		"  <id>  - The ID of the thread.\n", 0);
	add_debugger_command_etc("drop", &drop_into_debugger,
		"Drop a thread into the userland debugger",
		"<id>\n"
		"Drops the specified (userland) thread into the userland debugger\n"
		"after leaving the kernel debugger.\n"
		"  <id>  - The ID of the thread.\n", 0);
	add_debugger_command_etc("priority", &set_thread_prio,
		"Set a thread's priority",
		"<priority> [ <id> ]\n"
		"Sets the priority of the thread with the specified ID to the given\n"
		"priority. If no thread ID is given, the current thread is selected.\n"
		"  <priority>  - The thread's new priority (0 - 120)\n"
		"  <id>        - The ID of the thread.\n", 0);

	return B_OK;
}


status_t
thread_preboot_init_percpu(struct kernel_args *args, int32 cpuNum)
{
	// set up the cpu pointer in the not yet initialized per-cpu idle thread
	// so that get_current_cpu and friends will work, which is crucial for
	// a lot of low level routines
	sIdleThreads[cpuNum].cpu = &gCPU[cpuNum];
	arch_thread_set_current_thread(&sIdleThreads[cpuNum]);
	return B_OK;
}

//	#pragma mark - public kernel API


void
exit_thread(status_t returnValue)
{
	struct thread *thread = thread_get_current_thread();

	thread->exit.status = returnValue;
	thread->exit.reason = THREAD_RETURN_EXIT;

	// if called from a kernel thread, we don't deliver the signal,
	// we just exit directly to keep the user space behaviour of
	// this function
	if (thread->team != team_get_kernel_team())
		send_signal_etc(thread->id, SIGKILLTHR, B_DO_NOT_RESCHEDULE);
	else
		thread_exit();
}


status_t
kill_thread(thread_id id)
{
	if (id <= 0)
		return B_BAD_VALUE;

	return send_signal(id, SIGKILLTHR);
}


status_t
send_data(thread_id thread, int32 code, const void *buffer, size_t bufferSize)
{
	return send_data_etc(thread, code, buffer, bufferSize, 0);
}


int32
receive_data(thread_id *sender, void *buffer, size_t bufferSize)
{
	return receive_data_etc(sender, buffer, bufferSize, 0);
}


bool
has_data(thread_id thread)
{
	int32 count;

	if (get_sem_count(thread_get_current_thread()->msg.read_sem,
			&count) != B_OK)
		return false;

	return count == 0 ? false : true;
}


status_t
_get_thread_info(thread_id id, thread_info *info, size_t size)
{
	status_t status = B_OK;
	struct thread *thread;
	cpu_status state;

	if (info == NULL || size != sizeof(thread_info) || id < B_OK)
		return B_BAD_VALUE;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	thread = thread_get_thread_struct_locked(id);
	if (thread == NULL) {
		status = B_BAD_VALUE;
		goto err;
	}

	fill_thread_info(thread, info, size);

err:
	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	return status;
}


status_t
_get_next_thread_info(team_id team, int32 *_cookie, thread_info *info,
	size_t size)
{
	status_t status = B_BAD_VALUE;
	struct thread *thread = NULL;
	cpu_status state;
	int slot;
	thread_id lastThreadID;

	if (info == NULL || size != sizeof(thread_info) || team < B_OK)
		return B_BAD_VALUE;

	if (team == B_CURRENT_TEAM)
		team = team_get_current_team_id();
	else if (!team_is_valid(team))
		return B_BAD_VALUE;

	slot = *_cookie;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	lastThreadID = peek_next_thread_id();
	if (slot >= lastThreadID)
		goto err;

	while (slot < lastThreadID
		&& (!(thread = thread_get_thread_struct_locked(slot))
			|| thread->team->id != team))
		slot++;

	if (thread != NULL && thread->team->id == team) {
		fill_thread_info(thread, info, size);

		*_cookie = slot + 1;
		status = B_OK;
	}

err:
	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	return status;
}


thread_id
find_thread(const char *name)
{
	struct hash_iterator iterator;
	struct thread *thread;
	cpu_status state;

	if (name == NULL)
		return thread_get_current_thread_id();

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	// ToDo: this might not be in the same order as find_thread() in BeOS
	//		which could be theoretically problematic.
	// ToDo: scanning the whole list with the thread lock held isn't exactly
	//		cheap either - although this function is probably used very rarely.

	hash_open(sThreadHash, &iterator);
	while ((thread = (struct thread*)hash_next(sThreadHash, &iterator))
			!= NULL) {
		// Search through hash
		if (thread->name != NULL && !strcmp(thread->name, name)) {
			thread_id id = thread->id;

			RELEASE_THREAD_LOCK();
			restore_interrupts(state);
			return id;
		}
	}

	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	return B_NAME_NOT_FOUND;
}


status_t
rename_thread(thread_id id, const char *name)
{
	struct thread *thread = thread_get_current_thread();
	status_t status = B_BAD_THREAD_ID;
	cpu_status state;

	if (name == NULL)
		return B_BAD_VALUE;

	state = disable_interrupts();
	GRAB_THREAD_LOCK();

	if (thread->id != id)
		thread = thread_get_thread_struct_locked(id);

	if (thread != NULL) {
		if (thread->team == thread_get_current_thread()->team) {
			strlcpy(thread->name, name, B_OS_NAME_LENGTH);
			status = B_OK;
		} else
			status = B_NOT_ALLOWED;
	}

	RELEASE_THREAD_LOCK();
	restore_interrupts(state);

	return status;
}


status_t
set_thread_priority(thread_id id, int32 priority)
{
	struct thread *thread;
	int32 oldPriority;

	// make sure the passed in priority is within bounds
	if (priority > B_MAX_PRIORITY)
		priority = B_MAX_PRIORITY;
	if (priority < B_MIN_PRIORITY)
		priority = B_MIN_PRIORITY;

	thread = thread_get_current_thread();
	if (thread->id == id) {
		// it's ourself, so we know we aren't in the run queue, and we can manipulate
		// our structure directly
		oldPriority = thread->priority;
			// note that this might not return the correct value if we are preempted
			// here, and another thread changes our priority before the next line is
			// executed
		thread->priority = thread->next_priority = priority;
	} else {
		cpu_status state = disable_interrupts();
		GRAB_THREAD_LOCK();

		thread = thread_get_thread_struct_locked(id);
		if (thread) {
			oldPriority = thread->priority;
			thread->next_priority = priority;
			if (thread->state == B_THREAD_READY && thread->priority != priority) {
				// if the thread is in the run queue, we reinsert it at a new position
				scheduler_remove_from_run_queue(thread);
				thread->priority = priority;
				scheduler_enqueue_in_run_queue(thread);
			} else
				thread->priority = priority;
		} else
			oldPriority = B_BAD_THREAD_ID;

		RELEASE_THREAD_LOCK();
		restore_interrupts(state);
	}

	return oldPriority;
}


status_t
snooze_etc(bigtime_t timeout, int timebase, uint32 flags)
{
	status_t status;

	if (timebase != B_SYSTEM_TIMEBASE)
		return B_BAD_VALUE;

	status = acquire_sem_etc(sSnoozeSem, 1, flags, timeout);
	if (status == B_TIMED_OUT || status == B_WOULD_BLOCK)
		return B_OK;

	return status;
}


/*!	snooze() for internal kernel use only; doesn't interrupt on signals. */
status_t
snooze(bigtime_t timeout)
{
	return snooze_etc(timeout, B_SYSTEM_TIMEBASE, B_RELATIVE_TIMEOUT);
}


/*!
	snooze_until() for internal kernel use only; doesn't interrupt on
	signals.
*/
status_t
snooze_until(bigtime_t timeout, int timebase)
{
	return snooze_etc(timeout, timebase, B_ABSOLUTE_TIMEOUT);
}


status_t
wait_for_thread(thread_id thread, status_t *_returnCode)
{
	return wait_for_thread_etc(thread, 0, 0, _returnCode);
}


status_t
suspend_thread(thread_id id)
{
	if (id <= 0)
		return B_BAD_VALUE;

	return send_signal(id, SIGSTOP);
}


status_t
resume_thread(thread_id id)
{
	if (id <= 0)
		return B_BAD_VALUE;

	return send_signal_etc(id, SIGCONT, SIGNAL_FLAG_DONT_RESTART_SYSCALL);
		// This retains compatibility to BeOS which documents the
		// combination of suspend_thread() and resume_thread() to
		// interrupt threads waiting on semaphores.
}


thread_id
spawn_kernel_thread(thread_func function, const char *name, int32 priority,
	void *arg)
{
	return create_thread(name, team_get_kernel_team()->id,
		(thread_entry_func)function, arg, NULL, priority, true, -1);
}


/* TODO: split this; have kernel version set kerrno */
int
getrlimit(int resource, struct rlimit * rlp)
{
	if (!rlp)
		return B_BAD_ADDRESS;

	switch (resource) {
		case RLIMIT_NOFILE:
		case RLIMIT_NOVMON:
			return vfs_getrlimit(resource, rlp);

		case RLIMIT_STACK:
		{
			struct thread *thread = thread_get_current_thread();
			if (!thread)
				return B_ERROR;
			rlp->rlim_cur = thread->user_stack_size;
			rlp->rlim_max = thread->user_stack_size;
			return 0;
		}

		default:
			return EINVAL;
	}

	return 0;
}


/* TODO: split this; have kernel version set kerrno */
int
setrlimit(int resource, const struct rlimit * rlp)
{
	if (!rlp)
		return B_BAD_ADDRESS;

	switch (resource) {
		case RLIMIT_NOFILE:
		case RLIMIT_NOVMON:
			return vfs_setrlimit(resource, rlp);

		default:
			return EINVAL;
	}

	return 0;
}


//	#pragma mark - syscalls


void
_user_exit_thread(status_t returnValue)
{
	exit_thread(returnValue);
}


status_t
_user_kill_thread(thread_id thread)
{
	return kill_thread(thread);
}


status_t
_user_resume_thread(thread_id thread)
{
	return resume_thread(thread);
}


status_t
_user_suspend_thread(thread_id thread)
{
	return suspend_thread(thread);
}


status_t
_user_rename_thread(thread_id thread, const char *userName)
{
	char name[B_OS_NAME_LENGTH];

	if (!IS_USER_ADDRESS(userName)
		|| userName == NULL
		|| user_strlcpy(name, userName, B_OS_NAME_LENGTH) < B_OK)
		return B_BAD_ADDRESS;

	return rename_thread(thread, name);
}


int32
_user_set_thread_priority(thread_id thread, int32 newPriority)
{
	return set_thread_priority(thread, newPriority);
}


thread_id
_user_spawn_thread(int32 (*entry)(thread_func, void *), const char *userName,
	int32 priority, void *data1, void *data2)
{
	char name[B_OS_NAME_LENGTH];
	thread_id threadID;

	if (!IS_USER_ADDRESS(entry) || entry == NULL
		|| (userName != NULL && (!IS_USER_ADDRESS(userName)
			|| user_strlcpy(name, userName, B_OS_NAME_LENGTH) < B_OK)))
		return B_BAD_ADDRESS;

	threadID = create_thread(userName != NULL ? name : "user thread",
		thread_get_current_thread()->team->id, entry,
		data1, data2, priority, false, -1);

	user_debug_thread_created(threadID);

	return threadID;
}


status_t
_user_snooze_etc(bigtime_t timeout, int timebase, uint32 flags)
{
	// NOTE: We only know the system timebase at the moment.
	syscall_restart_handle_timeout_pre(flags, timeout);

	status_t error = snooze_etc(timeout, timebase, flags | B_CAN_INTERRUPT);

	return syscall_restart_handle_timeout_post(error, timeout);
}


void
_user_thread_yield(void)
{
	thread_yield(true);
}


status_t
_user_get_thread_info(thread_id id, thread_info *userInfo)
{
	thread_info info;
	status_t status;

	if (!IS_USER_ADDRESS(userInfo))
		return B_BAD_ADDRESS;

	status = _get_thread_info(id, &info, sizeof(thread_info));

	if (status >= B_OK
		&& user_memcpy(userInfo, &info, sizeof(thread_info)) < B_OK)
		return B_BAD_ADDRESS;

	return status;
}


status_t
_user_get_next_thread_info(team_id team, int32 *userCookie,
	thread_info *userInfo)
{
	status_t status;
	thread_info info;
	int32 cookie;

	if (!IS_USER_ADDRESS(userCookie) || !IS_USER_ADDRESS(userInfo)
		|| user_memcpy(&cookie, userCookie, sizeof(int32)) < B_OK)
		return B_BAD_ADDRESS;

	status = _get_next_thread_info(team, &cookie, &info, sizeof(thread_info));
	if (status < B_OK)
		return status;

	if (user_memcpy(userCookie, &cookie, sizeof(int32)) < B_OK
		|| user_memcpy(userInfo, &info, sizeof(thread_info)) < B_OK)
		return B_BAD_ADDRESS;

	return status;
}


thread_id
_user_find_thread(const char *userName)
{
	char name[B_OS_NAME_LENGTH];

	if (userName == NULL)
		return find_thread(NULL);

	if (!IS_USER_ADDRESS(userName)
		|| user_strlcpy(name, userName, sizeof(name)) < B_OK)
		return B_BAD_ADDRESS;

	return find_thread(name);
}


status_t
_user_wait_for_thread(thread_id id, status_t *userReturnCode)
{
	status_t returnCode;
	status_t status;

	if (userReturnCode != NULL && !IS_USER_ADDRESS(userReturnCode))
		return B_BAD_ADDRESS;

	status = wait_for_thread_etc(id, B_CAN_INTERRUPT, 0, &returnCode);

	if (status == B_OK && userReturnCode != NULL
		&& user_memcpy(userReturnCode, &returnCode, sizeof(status_t)) < B_OK) {
		return B_BAD_ADDRESS;
	}

	return syscall_restart_handle_post(status);
}


bool
_user_has_data(thread_id thread)
{
	return has_data(thread);
}


status_t
_user_send_data(thread_id thread, int32 code, const void *buffer,
	size_t bufferSize)
{
	if (!IS_USER_ADDRESS(buffer))
		return B_BAD_ADDRESS;

	return send_data_etc(thread, code, buffer, bufferSize,
		B_KILL_CAN_INTERRUPT);
		// supports userland buffers
}


status_t
_user_receive_data(thread_id *_userSender, void *buffer, size_t bufferSize)
{
	thread_id sender;
	status_t code;

	if (!IS_USER_ADDRESS(_userSender)
		|| !IS_USER_ADDRESS(buffer))
		return B_BAD_ADDRESS;

	code = receive_data_etc(&sender, buffer, bufferSize, B_KILL_CAN_INTERRUPT);
		// supports userland buffers

	if (user_memcpy(_userSender, &sender, sizeof(thread_id)) < B_OK)
		return B_BAD_ADDRESS;

	return code;
}


// ToDo: the following two functions don't belong here


int
_user_getrlimit(int resource, struct rlimit *urlp)
{
	struct rlimit rl;
	int ret;

	if (urlp == NULL)
		return EINVAL;

	if (!IS_USER_ADDRESS(urlp))
		return B_BAD_ADDRESS;

	ret = getrlimit(resource, &rl);

	if (ret == 0) {
		ret = user_memcpy(urlp, &rl, sizeof(struct rlimit));
		if (ret < 0)
			return ret;

		return 0;
	}

	return ret;
}


int
_user_setrlimit(int resource, const struct rlimit *userResourceLimit)
{
	struct rlimit resourceLimit;

	if (userResourceLimit == NULL)
		return EINVAL;

	if (!IS_USER_ADDRESS(userResourceLimit)
		|| user_memcpy(&resourceLimit, userResourceLimit,
			sizeof(struct rlimit)) < B_OK)
		return B_BAD_ADDRESS;

	return setrlimit(resource, &resourceLimit);
}