sched: enforce ref-counting on current task/thread pointers

arch/x86_64/panic.c

@@ -217,16 +217,18 @@ static void print_stack_trace(
 
 void ml_print_stack_trace(uintptr_t ip)
 {
-	struct task *task = current_task();
+	struct task *task = get_current_task();
 	struct address_space *space = task ? task->t_address_space : NULL;
 	uintptr_t bp;
 	asm volatile("mov %%rbp, %0" : "=r"(bp));
 	print_stack_trace(space, ip, bp);
+	put_current_task(task);
 }
 
 void ml_print_stack_trace_irq(struct ml_cpu_context *ctx)
 {
-	struct task *task = current_task();
+	struct task *task = get_current_task();
 	struct address_space *space = task ? task->t_address_space : NULL;
 	print_stack_trace(space, ctx->rip, ctx->rbp);
+	put_current_task(task);
 }

arch/x86_64/pmap.c

@@ -496,11 +496,7 @@ kern_status_t pmap_handle_fault(
 {
 	// log_fault(fault_addr, flags);
 
-	if (flags & PMAP_FAULT_PRESENT) {
-		return KERN_FATAL_ERROR;
-	}
-
-	struct task *task = current_task();
+	struct task *task = get_current_task();
 	if (!task) {
 		return KERN_FATAL_ERROR;
 	}
@@ -511,7 +507,11 @@ kern_status_t pmap_handle_fault(
 	}
 
 	/* this must be called with `space` unlocked. */
-	return address_space_demand_map(space, fault_addr, flags);
+	kern_status_t status
+		= address_space_demand_map(space, fault_addr, flags);
+
+	put_current_task(task);
+	return status;
 }
 
 kern_status_t pmap_add(

arch/x86_64/thread.c

@@ -95,25 +95,30 @@ kern_status_t ml_thread_config_set(
 	const void *ptr,
 	size_t len)
 {
+	struct thread *self = get_current_thread();
+	kern_status_t status = KERN_OK;
+
 	switch (key) {
 	case THREAD_CFG_FSBASE:
 		if (len != sizeof(thread->tr_ml.tr_fsbase)) {
-			return KERN_INVALID_ARGUMENT;
+			status = KERN_INVALID_ARGUMENT;
+			break;
 		}
 
 		thread->tr_ml.tr_fsbase = *(virt_addr_t *)ptr;
-		if (thread == current_thread()) {
+		if (thread == self) {
 			wrmsr(MSR_FS_BASE, thread->tr_ml.tr_fsbase);
 		}
 
 		break;
 	case THREAD_CFG_GSBASE:
 		if (len != sizeof(thread->tr_ml.tr_gsbase)) {
-			return KERN_INVALID_ARGUMENT;
+			status = KERN_INVALID_ARGUMENT;
+			break;
 		}
 
 		thread->tr_ml.tr_gsbase = *(virt_addr_t *)ptr;
-		if (thread == current_thread()) {
+		if (thread == self) {
 			/* we're in the kernel right now, so the user and kernel
 			 * gs-base registers are swapped. when we return to
 			 * usermode, this value will be swapped back into
@@ -123,8 +128,10 @@ kern_status_t ml_thread_config_set(
 
 		break;
 	default:
-		return KERN_INVALID_ARGUMENT;
+		status = KERN_INVALID_ARGUMENT;
+		break;
 	}
 
-	return KERN_OK;
+	put_current_thread(self);
+	return status;
 }

include/kernel/sched.h

@@ -76,8 +76,10 @@ extern struct runqueue *cpu_rq(unsigned int cpu);
 extern cycles_t default_quantum(void);
 
 extern bool need_resched(void);
-extern struct task *current_task(void);
-extern struct thread *current_thread(void);
+extern struct task *get_current_task(void);
+extern struct thread *get_current_thread(void);
+extern void put_current_task(struct task *task);
+extern void put_current_thread(struct thread *thread);
 
 extern struct runqueue *select_rq_for_thread(struct thread *thr);
 extern void schedule_thread_on_cpu(struct thread *thr);

init/main.c

@@ -44,8 +44,8 @@ static void hang(void)
 
 void background_thread(void)
 {
-	struct task *self = current_task();
-	struct thread *thread = current_thread();
+	struct task *self = get_current_task();
+	struct thread *thread = get_current_thread();
 	printk("background_thread() running on processor %u", this_cpu());
 	milli_sleep(1000);
 

kernel/channel.c

@@ -139,7 +139,6 @@ extern kern_status_t channel_recv_msg(
 	kern_msg_t *out_msg,
 	unsigned long *irq_flags)
 {
-	struct thread *self = current_thread();
 	struct msg *msg = NULL;
 	unsigned long msg_lock_flags;
 
@@ -170,7 +169,7 @@ extern kern_status_t channel_recv_msg(
 	}
 
 	struct task *sender = msg->msg_sender_thread->tr_parent;
-	struct task *receiver = self->tr_parent;
+	struct task *receiver = get_current_task();
 
 	struct address_space *src = sender->t_address_space,
 			     *dst = receiver->t_address_space;
@@ -192,6 +191,7 @@ extern kern_status_t channel_recv_msg(
 
 	if (status != KERN_OK) {
 		kmsg_reply_error(msg, status, &msg_lock_flags);
+		put_current_task(receiver);
 		return status;
 	}
 
@@ -216,6 +216,7 @@ extern kern_status_t channel_recv_msg(
 		&receiver->t_handles_lock,
 		f);
 	address_space_unlock_pair_irqrestore(src, dst, f);
+	put_current_task(receiver);
 
 	if (status != KERN_OK) {
 		kmsg_reply_error(msg, status, &msg_lock_flags);
@@ -250,11 +251,10 @@ extern kern_status_t channel_reply_msg(
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	struct thread *self = current_thread();
 	/* the task that is about to receive the response */
 	struct task *receiver = msg->msg_sender_thread->tr_parent;
 	/* the task that is about to send the response */
-	struct task *sender = self->tr_parent;
+	struct task *sender = get_current_task();
 
 	struct address_space *src = sender->t_address_space,
 			     *dst = receiver->t_address_space;
@@ -275,6 +275,7 @@ extern kern_status_t channel_reply_msg(
 
 	if (status != KERN_OK) {
 		kmsg_reply_error(msg, status, &msg_lock_flags);
+		put_current_task(sender);
 		return status;
 	}
 
@@ -299,6 +300,7 @@ extern kern_status_t channel_reply_msg(
 		&receiver->t_handles_lock,
 		f);
 	address_space_unlock_pair_irqrestore(src, dst, f);
+	put_current_task(sender);
 
 	if (status != KERN_OK) {
 		kmsg_reply_error(msg, status, &msg_lock_flags);

kernel/futex.c

@@ -32,8 +32,10 @@ static kern_status_t get_data(
 {
 	spin_lock_t *lock = NULL;
 	struct btree *futex_list = NULL;
+	struct task *self = NULL;
+
 	if (flags & FUTEX_PRIVATE) {
-		struct task *self = current_task();
+		self = get_current_task();
 		lock = &self->t_base.ob_lock;
 		futex_list = &self->t_futex;
 	} else if (flags & FUTEX_SHARED) {
@@ -48,12 +50,20 @@ static kern_status_t get_data(
 
 	if (!futex && !(flags & FUTEX_CREATE)) {
 		spin_unlock_irqrestore(lock, *irq_flags);
+		if (self) {
+			put_current_task(self);
+		}
+
 		return KERN_NO_ENTRY;
 	}
 
 	futex = vm_cache_alloc(&futex_cache, VM_NORMAL);
 	if (!futex) {
 		spin_unlock_irqrestore(lock, *irq_flags);
+		if (self) {
+			put_current_task(self);
+		}
+
 		return KERN_NO_MEMORY;
 	}
 
@@ -61,6 +71,10 @@ static kern_status_t get_data(
 
 	put_futex(futex_list, futex);
 
+	if (self) {
+		put_current_task(self);
+	}
+
 	*out = futex;
 	*out_lock = lock;
 	return KERN_OK;
@@ -68,9 +82,10 @@ static kern_status_t get_data(
 
 static kern_status_t cleanup_data(struct futex *futex, unsigned int flags)
 {
+	struct task *self = NULL;
 	struct btree *futex_list = NULL;
 	if (flags & FUTEX_PRIVATE) {
-		struct task *self = current_task();
+		self = get_current_task();
 		futex_list = &self->t_futex;
 	} else if (flags & FUTEX_SHARED) {
 		futex_list = &shared_futex_list;
@@ -81,12 +96,16 @@ static kern_status_t cleanup_data(struct futex *futex, unsigned int flags)
 	btree_delete(futex_list, &futex->f_node);
 	vm_cache_free(&futex_cache, futex);
 
+	if (self) {
+		put_current_task(self);
+	}
+
 	return KERN_OK;
 }
 
 static kern_status_t futex_get_shared(kern_futex_t *futex, futex_key_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	struct address_space *space = self->t_address_space;
 
 	unsigned long flags;
@@ -97,6 +116,7 @@ static kern_status_t futex_get_shared(kern_futex_t *futex, futex_key_t *out)
 		out,
 		&flags);
 	address_space_unlock_irqrestore(space, flags);
+	put_current_task(self);
 	return status;
 }
 

kernel/object.c

@@ -175,7 +175,7 @@ void object_wait_signal(
 	uint32_t signals,
 	unsigned long *irq_flags)
 {
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 	struct wait_item waiter;
 	wait_item_init(&waiter, self);
 	for (;;) {
@@ -189,4 +189,5 @@ void object_wait_signal(
 		object_lock_irqsave(obj, irq_flags);
 	}
 	thread_wait_end(&waiter, &obj->ob_wq);
+	put_current_thread(self);
 }

kernel/panic.c

@@ -19,8 +19,8 @@ void panic_irq(struct ml_cpu_context *ctx, const char *fmt, ...)
 	printk("---[ kernel panic: %s", buf);
 	printk("kernel: " BUILD_ID ", compiler version: " __VERSION__);
 
-	struct task *task = current_task();
-	struct thread *thr = current_thread();
+	struct task *task = get_current_task();
+	struct thread *thr = get_current_thread();
 
 	if (task && thr) {
 		printk("task: %s (id: %d, thread: %d)",
@@ -31,6 +31,9 @@ void panic_irq(struct ml_cpu_context *ctx, const char *fmt, ...)
 		printk("task: [bootstrap]");
 	}
 
+	put_current_thread(thr);
+	put_current_task(task);
+
 	printk("cpu: %u", this_cpu());
 
 	ml_print_cpu_state(ctx);

kernel/port.c

@@ -37,7 +37,7 @@ struct port *port_cast(struct object *obj)
 static void wait_for_reply(struct msg *msg, unsigned long *lock_flags)
 {
 	struct wait_item waiter;
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 
 	wait_item_init(&waiter, self);
 	for (;;) {
@@ -52,6 +52,7 @@ static void wait_for_reply(struct msg *msg, unsigned long *lock_flags)
 	}
 
 	self->tr_state = THREAD_READY;
+	put_current_thread(self);
 }
 
 struct port *port_create(void)
@@ -83,9 +84,12 @@ kern_status_t port_connect(struct port *port, struct channel *remote)
 	msg->msg_status = KMSG_ASYNC;
 	msg->msg_type = KERN_MSG_TYPE_EVENT;
 	msg->msg_event = KERN_MSG_EVENT_CONNECTION;
-	msg->msg_sender_thread_id = current_thread()->tr_id;
 	msg->msg_sender_port_id = port->p_base.ob_id;
 
+	struct thread *self = get_current_thread();
+	msg->msg_sender_thread_id = self->tr_id;
+	put_current_thread(self);
+
 	unsigned long flags;
 	channel_lock_irqsave(remote, &flags);
 	channel_enqueue_msg(remote, msg);
@@ -112,9 +116,12 @@ kern_status_t port_disconnect(struct port *port)
 	msg->msg_status = KMSG_ASYNC;
 	msg->msg_type = KERN_MSG_TYPE_EVENT;
 	msg->msg_event = KERN_MSG_EVENT_DISCONNECTION;
-	msg->msg_sender_thread_id = current_thread()->tr_id;
 	msg->msg_sender_port_id = port->p_base.ob_id;
 
+	struct thread *self = get_current_thread();
+	msg->msg_sender_thread_id = self->tr_id;
+	put_current_thread(self);
+
 	unsigned long flags;
 	channel_lock_irqsave(port->p_remote, &flags);
 	channel_enqueue_msg(port->p_remote, msg);
@@ -136,7 +143,7 @@ kern_status_t port_send_msg(
 		return KERN_BAD_STATE;
 	}
 
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 	struct msg msg;
 	memset(&msg, 0x0, sizeof msg);
 	msg.msg_type = KERN_MSG_TYPE_DATA;
@@ -156,6 +163,7 @@ kern_status_t port_send_msg(
 	channel_lock_irqsave(port->p_remote, &flags);
 	btree_delete(&port->p_remote->c_msg, &msg.msg_node);
 	channel_unlock_irqrestore(port->p_remote, flags);
+	put_current_thread(self);
 
 	return msg.msg_result;
 }

sched/core.c

@@ -215,18 +215,19 @@ void schedule_thread_on_cpu(struct thread *thr)
 
 void start_charge_period(void)
 {
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 	if (!self) {
 		return;
 	}
 
 	self->tr_charge_period_start = get_cycles();
+	put_current_thread(self);
 }
 
 void end_charge_period(void)
 {
 	preempt_disable();
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 	if (!self) {
 		return;
 	}
@@ -244,6 +245,7 @@ void end_charge_period(void)
 	}
 
 	self->tr_charge_period_start = 0;
+	put_current_thread(self);
 
 	// printk("%llu cycles charged to %s/%u", charge,
 	// self->tr_parent->t_name, self->tr_parent->t_id);

sched/task.c

@@ -282,7 +282,7 @@ struct task *task_from_tid(tid_t id)
 
 void task_exit(int status)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	unsigned long flags;
 	task_lock_irqsave(self, &flags);
 	struct task *parent = self->t_parent;
@@ -295,7 +295,7 @@ void task_exit(int status)
 		task_unlock(parent);
 	}
 
-	struct thread *cur_thread = current_thread();
+	struct thread *cur_thread = get_current_thread();
 
 	self->t_state = TASK_STOPPED;
 	cur_thread->tr_state = THREAD_STOPPED;
@@ -340,6 +340,9 @@ void task_exit(int status)
 	       self->t_base.ob_refcount);
 	spin_unlock_irqrestore(handles_lock, flags);
 
+	put_current_thread(cur_thread);
+	put_current_task(self);
+
 	while (1) {
 		schedule(SCHED_NORMAL);
 	}
@@ -410,8 +413,19 @@ struct thread *task_create_thread(struct task *parent)
 	return thread;
 }
 
-struct task *current_task(void)
+struct task *get_current_task(void)
 {
-	struct thread *thr = current_thread();
-	return thr ? thr->tr_parent : NULL;
+	struct thread *thr = get_current_thread();
+	if (!thr) {
+		return NULL;
+	}
+
+	struct task *out = task_ref(thr->tr_parent);
+	put_current_thread(thr);
+	return out;
+}
+
+void put_current_task(struct task *task)
+{
+	task_unref(task);
 }

sched/thread.c

@@ -105,7 +105,7 @@ void thread_free(struct thread *thr)
 {
 }
 
-struct thread *current_thread(void)
+struct thread *get_current_thread(void)
 {
 	struct cpu_data *cpu = get_this_cpu();
 	if (!cpu) {
@@ -113,13 +113,24 @@ struct thread *current_thread(void)
 	}
 
 	struct thread *out = cpu->c_rq.rq_cur;
+	object_ref(&out->tr_base);
+
 	put_cpu(cpu);
 	return out;
 }
 
+void put_current_thread(struct thread *thr)
+{
+	object_unref(&thr->tr_base);
+}
+
 bool need_resched(void)
 {
-	return (current_thread()->tr_flags & THREAD_F_NEED_RESCHED) != 0;
+	struct thread *thr = get_current_thread();
+	bool result = (thr->tr_flags & THREAD_F_NEED_RESCHED) != 0;
+	put_current_thread(thr);
+
+	return result;
 }
 
 int thread_priority(struct thread *thr)
@@ -143,7 +154,7 @@ void thread_awaken(struct thread *thr)
 
 void thread_exit(void)
 {
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 	unsigned long flags;
 	thread_lock_irqsave(self, &flags);
 	self->tr_state = THREAD_STOPPED;
@@ -153,6 +164,7 @@ void thread_exit(void)
 	       self->tr_parent->t_id,
 	       self->tr_id);
 	thread_unlock_irqrestore(self, flags);
+	put_current_thread(self);
 
 	while (1) {
 		schedule(SCHED_NORMAL);

sched/timer.c

@@ -44,7 +44,7 @@ unsigned long schedule_timeout(unsigned long ticks)
 {
 	struct timer timer;
 
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 
 	timer.t_entry = QUEUE_ENTRY_INIT;
 	timer.t_expiry = clock_ticks + ticks;
@@ -58,6 +58,7 @@ unsigned long schedule_timeout(unsigned long ticks)
 	schedule(SCHED_NORMAL);
 
 	remove_timer(&timer);
+	put_current_thread(self);
 
 	return 0;
 }

sched/wait.c

@@ -110,7 +110,7 @@ void wakeup_one(struct waitqueue *q)
 
 void sleep_forever(void)
 {
-	struct thread *thr = current_thread();
+	struct thread *thr = get_current_thread();
 	struct runqueue *rq = thr->tr_rq;
 
 	unsigned long flags;
@@ -121,7 +121,17 @@ void sleep_forever(void)
 
 	rq_unlock(rq, flags);
 
-	while (thr->tr_state == THREAD_SLEEPING) {
+	put_current_thread(thr);
+
+	while (1) {
+		thr = get_current_thread();
+		bool sleep = (thr->tr_state == THREAD_SLEEPING);
+		put_current_thread(thr);
+
+		if (!sleep) {
+			break;
+		}
+
 		schedule(SCHED_NORMAL);
 	}
 }

syscall/address-space.c

@@ -11,13 +11,15 @@ kern_status_t sys_address_space_read(
 	size_t count,
 	size_t *nr_read)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, dst, count)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (nr_read && !validate_access_w(self, nr_read, sizeof *nr_read)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -30,12 +32,14 @@ kern_status_t sys_address_space_read(
 		= task_resolve_handle(self, region_handle, &obj, &handle_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -52,6 +56,7 @@ kern_status_t sys_address_space_read(
 	address_space_unlock_irqrestore(region, flags);
 
 	object_unref(obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -63,14 +68,16 @@ kern_status_t sys_address_space_write(
 	size_t count,
 	size_t *nr_written)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_r(self, src, count)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (nr_written
 	    && !validate_access_w(self, nr_written, sizeof *nr_written)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -83,12 +90,14 @@ kern_status_t sys_address_space_write(
 		= task_resolve_handle(self, region_handle, &obj, &handle_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -105,6 +114,7 @@ kern_status_t sys_address_space_write(
 	address_space_unlock_irqrestore(region, flags);
 
 	object_unref(obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -118,13 +128,14 @@ kern_status_t sys_address_space_map(
 	vm_prot_t prot,
 	virt_addr_t *out_base_address)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (out_base_address
 	    && !validate_access_r(
 		    self,
 		    out_base_address,
 		    sizeof *out_base_address)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -141,24 +152,28 @@ kern_status_t sys_address_space_map(
 		&region_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	status = task_resolve_handle(self, object_handle, &vmo_obj, &vmo_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(region_obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
 	struct vm_object *vmo = vm_object_cast(vmo_obj);
 	if (!vmo) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -177,6 +192,7 @@ kern_status_t sys_address_space_map(
 
 	object_unref(vmo_obj);
 	object_unref(region_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -186,7 +202,7 @@ kern_status_t sys_address_space_unmap(
 	virt_addr_t base,
 	size_t length)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	kern_status_t status = KERN_OK;
 	unsigned long flags;
@@ -201,12 +217,14 @@ kern_status_t sys_address_space_unmap(
 		&region_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(region_obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -215,6 +233,7 @@ kern_status_t sys_address_space_unmap(
 	status = address_space_unmap(region, base, length);
 
 	object_unref(region_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -225,13 +244,14 @@ kern_status_t sys_address_space_reserve(
 	size_t length,
 	virt_addr_t *out_base_address)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (out_base_address
 	    && !validate_access_r(
 		    self,
 		    out_base_address,
 		    sizeof *out_base_address)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -248,12 +268,14 @@ kern_status_t sys_address_space_reserve(
 		&region_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(region_obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -268,6 +290,7 @@ kern_status_t sys_address_space_reserve(
 	address_space_unlock_irqrestore(region, flags);
 
 	object_unref(region_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -277,7 +300,7 @@ kern_status_t sys_address_space_release(
 	virt_addr_t base,
 	size_t length)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	kern_status_t status = KERN_OK;
 	unsigned long flags;
@@ -292,12 +315,14 @@ kern_status_t sys_address_space_release(
 		&region_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	struct address_space *region = address_space_cast(region_obj);
 	if (!region) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -308,6 +333,7 @@ kern_status_t sys_address_space_release(
 	address_space_unlock_irqrestore(region, flags);
 
 	object_unref(region_obj);
+	put_current_task(self);
 
 	return status;
 }

syscall/config.c

@@ -3,21 +3,26 @@
 
 kern_status_t sys_kern_config_get(kern_config_key_t key, void *ptr, size_t len)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
+	kern_status_t status = KERN_OK;
 
 	switch (key) {
 	case KERN_CFG_PAGE_SIZE:
 		if (!validate_access_w(self, ptr, sizeof(uintptr_t))) {
-			return KERN_MEMORY_FAULT;
+			status = KERN_MEMORY_FAULT;
+			break;
 		}
 
 		*(uint32_t *)ptr = VM_PAGE_SIZE;
-		return KERN_OK;
+		status = KERN_OK;
+		break;
 	default:
-		return KERN_INVALID_ARGUMENT;
+		status = KERN_INVALID_ARGUMENT;
+		break;
 	}
 
-	return KERN_UNSUPPORTED;
+	put_current_task(self);
+	return status;
 }
 
 kern_status_t sys_kern_config_set(

syscall/futex.c

@@ -8,18 +8,22 @@ kern_status_t sys_futex_wait(
 	kern_futex_t new_val,
 	unsigned int flags)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_r(self, futex, sizeof *futex)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	futex_key_t key;
 	kern_status_t status = futex_get(futex, &key, flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
-	return futex_wait(key, new_val, flags);
+	status = futex_wait(key, new_val, flags);
+	put_current_task(self);
+	return status;
 }
 
 kern_status_t sys_futex_wake(

syscall/handle.c

@@ -3,9 +3,13 @@
 
 kern_status_t sys_kern_handle_close(kern_handle_t handle)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
-	return task_close_handle(self, handle);
+	kern_status_t status = task_close_handle(self, handle);
+
+	put_current_task(self);
+
+	return status;
 }
 
 kern_status_t sys_kern_handle_transfer(
@@ -24,10 +28,11 @@ kern_status_t sys_kern_handle_transfer(
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (out_handle
 	    && !validate_access_w(self, out_handle, sizeof *out_handle)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -120,6 +125,8 @@ kern_status_t sys_kern_handle_transfer(
 		*out_handle = dest_handle;
 	}
 
+	put_current_task(self);
+
 	return KERN_OK;
 
 cleanup:
@@ -135,5 +142,7 @@ cleanup:
 		object_unref(src_object);
 	}
 
+	put_current_task(self);
+
 	return status;
 }

syscall/log.c

@@ -6,9 +6,11 @@
 kern_status_t sys_kern_log(const char *s)
 {
 #ifdef TRACE
-	struct task *task = current_task();
-	struct thread *thread = current_thread();
+	struct task *task = get_current_task();
+	struct thread *thread = get_current_thread();
 	printk("%s[%d.%d]: %s", task->t_name, task->t_id, thread->tr_id, s);
+	put_current_thread(thread);
+	put_current_task(task);
 #else
 	printk("%s", s);
 #endif

syscall/msg.c

@@ -7,13 +7,15 @@
 
 kern_status_t sys_channel_create(unsigned int id, kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	struct channel *channel = channel_create();
 	if (!channel) {
+		put_current_task(self);
 		return KERN_NO_MEMORY;
 	}
 
@@ -22,6 +24,7 @@ kern_status_t sys_channel_create(unsigned int id, kern_handle_t *out)
 
 	if (task_get_channel(self, id)) {
 		task_unlock_irqrestore(self, irq_flags);
+		put_current_task(self);
 		return KERN_NAME_EXISTS;
 	}
 
@@ -31,11 +34,13 @@ kern_status_t sys_channel_create(unsigned int id, kern_handle_t *out)
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, irq_flags);
 		object_unref(&channel->c_base);
+		put_current_task(self);
 		return status;
 	}
 
 	task_add_channel(self, channel, id);
 	task_unlock_irqrestore(self, irq_flags);
+	put_current_task(self);
 
 	*out = handle;
 	return KERN_OK;
@@ -43,13 +48,15 @@ kern_status_t sys_channel_create(unsigned int id, kern_handle_t *out)
 
 kern_status_t sys_port_create(kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	struct port *port = port_create();
 	if (!port) {
+		put_current_task(self);
 		return KERN_NO_MEMORY;
 	}
 
@@ -61,6 +68,7 @@ kern_status_t sys_port_create(kern_handle_t *out)
 		= task_open_handle(self, &port->p_base, 0, &handle);
 	task_unlock_irqrestore(self, irq_flags);
 	object_unref(&port->p_base);
+	put_current_task(self);
 
 	if (status != KERN_OK) {
 		return status;
@@ -77,7 +85,7 @@ kern_status_t sys_port_connect(
 {
 	unsigned long flags;
 
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	task_lock_irqsave(self, &flags);
 
 	struct object *port_obj = NULL;
@@ -88,6 +96,7 @@ kern_status_t sys_port_connect(
 		&port_obj,
 		&port_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -96,6 +105,7 @@ kern_status_t sys_port_connect(
 
 	struct task *remote_task = task_from_tid(task_id);
 	if (!remote_task) {
+		put_current_task(self);
 		return KERN_NO_ENTRY;
 	}
 
@@ -104,6 +114,7 @@ kern_status_t sys_port_connect(
 	struct channel *remote = task_get_channel(remote_task, channel_id);
 	if (!remote) {
 		task_unlock_irqrestore(remote_task, flags);
+		put_current_task(self);
 		return KERN_NO_ENTRY;
 	}
 
@@ -115,6 +126,7 @@ kern_status_t sys_port_connect(
 	port_unlock_irqrestore(port, flags);
 	object_unref(&remote->c_base);
 	object_unref(port_obj);
+	put_current_task(self);
 
 	return KERN_OK;
 }
@@ -123,7 +135,7 @@ kern_status_t sys_port_disconnect(kern_handle_t port_handle)
 {
 	unsigned long flags;
 
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	task_lock_irqsave(self, &flags);
 
 	struct object *port_obj = NULL;
@@ -134,6 +146,7 @@ kern_status_t sys_port_disconnect(kern_handle_t port_handle)
 		&port_obj,
 		&port_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -142,6 +155,7 @@ kern_status_t sys_port_disconnect(kern_handle_t port_handle)
 	struct port *port = port_cast(port_obj);
 	if (!port) {
 		object_unref(port_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -149,6 +163,7 @@ kern_status_t sys_port_disconnect(kern_handle_t port_handle)
 	port_lock_irqsave(port, &flags);
 	status = port_disconnect(port);
 	port_unlock_irqrestore(port, flags);
+	put_current_task(self);
 
 	return status;
 }
@@ -219,13 +234,15 @@ kern_status_t sys_msg_send(
 	const kern_msg_t *msg,
 	kern_msg_t *out_reply)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_msg(self, msg, false)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_msg(self, out_reply, true)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -243,12 +260,14 @@ kern_status_t sys_msg_send(
 	task_unlock_irqrestore(self, flags);
 
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
 	struct port *port = port_cast(port_obj);
 	if (!port) {
 		object_unref(port_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -256,15 +275,17 @@ kern_status_t sys_msg_send(
 	status = port_send_msg(port, msg, out_reply, &flags);
 	port_unlock_irqrestore(port, flags);
 	object_unref(port_obj);
+	put_current_task(self);
 
 	return status;
 }
 
 kern_status_t sys_msg_recv(kern_handle_t channel_handle, kern_msg_t *out_msg)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_msg(self, out_msg, true)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -280,6 +301,7 @@ kern_status_t sys_msg_recv(kern_handle_t channel_handle, kern_msg_t *out_msg)
 		&channel_obj,
 		&channel_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -288,6 +310,7 @@ kern_status_t sys_msg_recv(kern_handle_t channel_handle, kern_msg_t *out_msg)
 	struct channel *channel = channel_cast(channel_obj);
 	if (!channel) {
 		object_unref(channel_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -295,6 +318,7 @@ kern_status_t sys_msg_recv(kern_handle_t channel_handle, kern_msg_t *out_msg)
 	status = channel_recv_msg(channel, out_msg, &flags);
 	channel_unlock_irqrestore(channel, flags);
 	object_unref(channel_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -304,9 +328,10 @@ kern_status_t sys_msg_reply(
 	msgid_t id,
 	const kern_msg_t *reply)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_msg(self, reply, true)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -322,6 +347,7 @@ kern_status_t sys_msg_reply(
 		&channel_obj,
 		&channel_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -330,6 +356,7 @@ kern_status_t sys_msg_reply(
 	struct channel *channel = channel_cast(channel_obj);
 	if (!channel) {
 		object_unref(channel_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -337,6 +364,7 @@ kern_status_t sys_msg_reply(
 	status = channel_reply_msg(channel, id, reply, &flags);
 	channel_unlock_irqrestore(channel, flags);
 	object_unref(channel_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -349,13 +377,15 @@ kern_status_t sys_msg_read(
 	size_t iov_count,
 	size_t *nr_read)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (nr_read && !validate_access_w(self, nr_read, sizeof *nr_read)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_iovec(self, iov, iov_count, true)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -371,6 +401,7 @@ kern_status_t sys_msg_read(
 		&channel_obj,
 		&channel_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -379,6 +410,7 @@ kern_status_t sys_msg_read(
 	struct channel *channel = channel_cast(channel_obj);
 	if (!channel) {
 		object_unref(channel_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -393,6 +425,7 @@ kern_status_t sys_msg_read(
 		nr_read);
 	channel_unlock_irqrestore(channel, flags);
 	object_unref(channel_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -405,14 +438,16 @@ kern_status_t sys_msg_write(
 	size_t iov_count,
 	size_t *nr_written)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (nr_written
 	    && !validate_access_w(self, nr_written, sizeof *nr_written)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_iovec(self, iov, iov_count, false)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -428,6 +463,7 @@ kern_status_t sys_msg_write(
 		&channel_obj,
 		&channel_handle_flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
@@ -436,6 +472,7 @@ kern_status_t sys_msg_write(
 	struct channel *channel = channel_cast(channel_obj);
 	if (!channel) {
 		object_unref(channel_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -450,6 +487,7 @@ kern_status_t sys_msg_write(
 		nr_written);
 	channel_unlock_irqrestore(channel, flags);
 	object_unref(channel_obj);
+	put_current_task(self);
 
 	return status;
 }

syscall/object.c

@@ -13,12 +13,13 @@ kern_status_t sys_kern_object_wait(kern_wait_item_t *items, size_t nr_items)
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	struct task *self = current_task();
-	struct thread *self_thread = current_thread();
+	struct task *self = get_current_task();
 	if (!validate_access_rw(self, items, nr_items * sizeof *items)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
+	struct thread *self_thread = get_current_thread();
 	self_thread->tr_state = THREAD_SLEEPING;
 
 	kern_status_t status = KERN_OK;
@@ -78,6 +79,9 @@ cleanup:
 	}
 
 	self_thread->tr_state = THREAD_READY;
+	put_current_thread(self_thread);
+	put_current_task(self);
+
 	return status;
 }
 
@@ -85,13 +89,15 @@ kern_status_t sys_kern_object_query(
 	kern_handle_t object_handle,
 	kern_object_info_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!out) {
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -100,12 +106,14 @@ kern_status_t sys_kern_object_query(
 	kern_status_t status
 		= task_resolve_handle(self, object_handle, &obj, &flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
 	out->obj_id = obj->ob_id;
 
 	object_unref(obj);
+	put_current_task(self);
 
 	return KERN_OK;
 }

syscall/task.c

@@ -9,8 +9,9 @@
 extern kern_status_t sys_task_exit(int status)
 {
 #if defined(TRACE)
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	printk("%s[%d]: task_exit(%d)", self->t_name, self->t_id, status);
+	put_current_task(self);
 #endif
 	task_exit(status);
 	return KERN_FATAL_ERROR;
@@ -18,8 +19,9 @@ extern kern_status_t sys_task_exit(int status)
 
 kern_status_t sys_task_self(kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -36,11 +38,13 @@ kern_status_t sys_task_self(kern_handle_t *out)
 	task_unlock_irqrestore(self, flags);
 
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
 	object_ref(&self->t_base);
 	handle_slot->h_object = &self->t_base;
+	put_current_task(self);
 
 	*out = handle;
 	return KERN_OK;
@@ -54,13 +58,15 @@ kern_status_t sys_task_create(
 	kern_handle_t *out_address_space)
 {
 	unsigned long flags;
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (name_len && !validate_access_r(self, name, name_len)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_access_w(self, out_task, sizeof *out_task)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -68,6 +74,7 @@ kern_status_t sys_task_create(
 		    self,
 		    out_address_space,
 		    sizeof *out_address_space)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -81,6 +88,7 @@ kern_status_t sys_task_create(
 		&parent_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -96,6 +104,7 @@ kern_status_t sys_task_create(
 	if (status != KERN_OK) {
 		object_unref(parent_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -108,6 +117,7 @@ kern_status_t sys_task_create(
 		object_unref(parent_obj);
 		handle_table_free_handle(self->t_handles, child_handle);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -121,6 +131,7 @@ kern_status_t sys_task_create(
 		handle_table_free_handle(self->t_handles, child_handle);
 		handle_table_free_handle(self->t_handles, space_handle);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 
 		return KERN_NO_MEMORY;
 	}
@@ -136,6 +147,7 @@ kern_status_t sys_task_create(
 	object_ref(&child->t_address_space->s_base);
 
 	object_unref(parent_obj);
+	put_current_task(self);
 
 	*out_task = child_handle;
 	*out_address_space = space_handle;
@@ -152,13 +164,15 @@ kern_status_t sys_task_create_thread(
 	kern_handle_t *out_thread)
 {
 	unsigned long flags;
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_r(self, args, nr_args * sizeof(uintptr_t))) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_access_w(self, out_thread, sizeof *out_thread)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -169,6 +183,7 @@ kern_status_t sys_task_create_thread(
 		= task_resolve_handle(self, task, &target_obj, &target_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -184,6 +199,7 @@ kern_status_t sys_task_create_thread(
 	if (status != KERN_OK) {
 		object_unref(target_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -198,6 +214,7 @@ kern_status_t sys_task_create_thread(
 		task_lock_irqsave(self, &flags);
 		handle_table_free_handle(self->t_handles, out_handle);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_NO_MEMORY;
 	}
 
@@ -207,6 +224,7 @@ kern_status_t sys_task_create_thread(
 
 	task_unlock_irqrestore(target, flags);
 	object_unref(target_obj);
+	put_current_task(self);
 
 	*out_thread = out_handle;
 	return KERN_OK;
@@ -216,8 +234,9 @@ kern_status_t sys_task_get_address_space(
 	kern_handle_t task_handle,
 	kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -235,6 +254,7 @@ kern_status_t sys_task_get_address_space(
 		&handle_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -246,6 +266,7 @@ kern_status_t sys_task_get_address_space(
 	if (status != KERN_OK) {
 		object_unref(task_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -255,6 +276,7 @@ kern_status_t sys_task_get_address_space(
 		object_unref(task_obj);
 		handle_table_free_handle(self->t_handles, handle);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -262,6 +284,7 @@ kern_status_t sys_task_get_address_space(
 	object_ref(&task->t_address_space->s_base);
 	task_unlock_irqrestore(self, flags);
 	object_unref(task_obj);
+	put_current_task(self);
 
 	*out = handle;
 	return KERN_OK;
@@ -269,12 +292,13 @@ kern_status_t sys_task_get_address_space(
 
 kern_status_t sys_thread_self(kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
-	struct thread *self_thread = current_thread();
+	struct thread *self_thread = get_current_thread();
 
 	unsigned long flags;
 	task_lock_irqsave(self, &flags);
@@ -289,11 +313,15 @@ kern_status_t sys_thread_self(kern_handle_t *out)
 	task_unlock_irqrestore(self, flags);
 
 	if (status != KERN_OK) {
+		put_current_thread(self_thread);
+		put_current_task(self);
 		return status;
 	}
 
 	object_ref(&self_thread->tr_base);
 	handle_slot->h_object = &self_thread->tr_base;
+	put_current_thread(self_thread);
+	put_current_task(self);
 
 	*out = handle;
 	return KERN_OK;
@@ -302,7 +330,7 @@ kern_status_t sys_thread_self(kern_handle_t *out)
 kern_status_t sys_thread_start(kern_handle_t thread_handle)
 {
 	unsigned long flags;
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	struct object *thread_obj;
 	handle_flags_t thread_flags;
@@ -314,6 +342,7 @@ kern_status_t sys_thread_start(kern_handle_t thread_handle)
 		&thread_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -322,6 +351,7 @@ kern_status_t sys_thread_start(kern_handle_t thread_handle)
 
 	schedule_thread_on_cpu(thread);
 	object_unref(thread_obj);
+	put_current_task(self);
 
 	return KERN_OK;
 }
@@ -340,9 +370,10 @@ kern_status_t sys_thread_config_get(
 	size_t len)
 {
 	unsigned long flags;
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, ptr, len)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -356,6 +387,7 @@ kern_status_t sys_thread_config_get(
 		&thread_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -365,6 +397,7 @@ kern_status_t sys_thread_config_get(
 	status = thread_config_get(thread, key, ptr, len);
 
 	object_unref(thread_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -376,9 +409,10 @@ kern_status_t sys_thread_config_set(
 	size_t len)
 {
 	unsigned long flags;
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, ptr, len)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -392,6 +426,7 @@ kern_status_t sys_thread_config_set(
 		&thread_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 

syscall/vm-controller.c

@@ -7,18 +7,21 @@
 
 kern_status_t sys_vm_controller_create(kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	struct vm_controller *ctrl = vm_controller_create();
 	if (!ctrl) {
+		put_current_task(self);
 		return KERN_NO_MEMORY;
 	}
 
 	kern_status_t status = task_open_handle(self, &ctrl->vc_base, 0, out);
+	put_current_task(self);
 	if (status != KERN_OK) {
 		object_unref(&ctrl->vc_base);
 		return status;
@@ -31,9 +34,10 @@ kern_status_t sys_vm_controller_recv(
 	kern_handle_t ctrl_handle,
 	equeue_packet_page_request_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -50,6 +54,7 @@ kern_status_t sys_vm_controller_recv(
 		&handle_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -57,6 +62,7 @@ kern_status_t sys_vm_controller_recv(
 	task_unlock_irqrestore(self, flags);
 	if (!ctrl) {
 		object_unref(ctrl_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -65,6 +71,7 @@ kern_status_t sys_vm_controller_recv(
 	vm_controller_unlock_irqrestore(ctrl, flags);
 
 	object_unref(ctrl_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -74,7 +81,7 @@ kern_status_t sys_vm_controller_recv_async(
 	kern_handle_t eq_handle,
 	equeue_key_t key)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	kern_status_t status = KERN_OK;
 	unsigned long flags;
@@ -85,6 +92,7 @@ kern_status_t sys_vm_controller_recv_async(
 	status = task_resolve_handle(self, ctrl_handle, &ctrl_obj, &ctrl_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -92,6 +100,7 @@ kern_status_t sys_vm_controller_recv_async(
 	if (status != KERN_OK) {
 		object_unref(ctrl_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -102,6 +111,7 @@ kern_status_t sys_vm_controller_recv_async(
 	if (!ctrl || !eq) {
 		object_unref(ctrl_obj);
 		object_unref(eq_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -111,6 +121,7 @@ kern_status_t sys_vm_controller_recv_async(
 
 	object_unref(ctrl_obj);
 	object_unref(eq_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -124,13 +135,15 @@ kern_status_t sys_vm_controller_create_object(
 	vm_prot_t prot,
 	kern_handle_t *out)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_r(self, name, name_len)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_access_w(self, out, sizeof *out)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -147,6 +160,7 @@ kern_status_t sys_vm_controller_create_object(
 		&handle_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -162,6 +176,7 @@ kern_status_t sys_vm_controller_create_object(
 	task_unlock_irqrestore(self, flags);
 	if (!ctrl) {
 		object_unref(ctrl_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -183,10 +198,12 @@ kern_status_t sys_vm_controller_create_object(
 		task_lock_irqsave(self, &flags);
 		handle_table_free_handle(self->t_handles, out_handle);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	out_slot->h_object = &out_vmo->vo_base;
+	put_current_task(self);
 
 	*out = out_handle;
 	return KERN_OK;
@@ -196,7 +213,7 @@ kern_status_t sys_vm_controller_detach_object(
 	kern_handle_t ctrl_handle,
 	kern_handle_t vmo_handle)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	kern_status_t status = KERN_OK;
 	unsigned long flags;
@@ -207,6 +224,7 @@ kern_status_t sys_vm_controller_detach_object(
 	status = task_resolve_handle(self, ctrl_handle, &ctrl_obj, &ctrl_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -214,6 +232,7 @@ kern_status_t sys_vm_controller_detach_object(
 	if (status != KERN_OK) {
 		object_unref(ctrl_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -224,6 +243,7 @@ kern_status_t sys_vm_controller_detach_object(
 	if (!ctrl || !vmo) {
 		object_unref(ctrl_obj);
 		object_unref(vmo_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -235,6 +255,7 @@ kern_status_t sys_vm_controller_detach_object(
 
 	object_unref(ctrl_obj);
 	object_unref(vmo_obj);
+	put_current_task(self);
 
 	return status;
 }
@@ -247,7 +268,7 @@ kern_status_t sys_vm_controller_supply_pages(
 	off_t src_offset,
 	size_t count)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	kern_status_t status = KERN_OK;
 	unsigned long flags;
@@ -258,6 +279,7 @@ kern_status_t sys_vm_controller_supply_pages(
 	status = task_resolve_handle(self, ctrl_handle, &ctrl_obj, &ctrl_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -265,6 +287,7 @@ kern_status_t sys_vm_controller_supply_pages(
 	if (status != KERN_OK) {
 		object_unref(ctrl_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -273,6 +296,7 @@ kern_status_t sys_vm_controller_supply_pages(
 		object_unref(ctrl_obj);
 		object_unref(dst_obj);
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
@@ -285,6 +309,7 @@ kern_status_t sys_vm_controller_supply_pages(
 		object_unref(ctrl_obj);
 		object_unref(dst_obj);
 		object_unref(src_obj);
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
@@ -303,6 +328,7 @@ kern_status_t sys_vm_controller_supply_pages(
 	object_unref(ctrl_obj);
 	object_unref(dst_obj);
 	object_unref(src_obj);
+	put_current_task(self);
 
 	return status;
 }

syscall/vm-object.c

@@ -11,13 +11,15 @@ kern_status_t sys_vm_object_create(
 	vm_prot_t prot,
 	kern_handle_t *out_handle)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if ((name || name_len) && !validate_access_r(self, name, name_len)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (!validate_access_w(self, out_handle, sizeof *out_handle)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -30,6 +32,7 @@ kern_status_t sys_vm_object_create(
 	kern_status_t status
 		= task_open_handle(self, &obj->vo_base, 0, out_handle);
 	object_unref(&obj->vo_base);
+	put_current_task(self);
 
 	return status;
 }
@@ -41,13 +44,15 @@ kern_status_t sys_vm_object_read(
 	size_t count,
 	size_t *nr_read)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_w(self, dst, count)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (nr_read && !validate_access_w(self, nr_read, sizeof *nr_read)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -55,15 +60,19 @@ kern_status_t sys_vm_object_read(
 	handle_flags_t flags = 0;
 	kern_status_t status = task_resolve_handle(self, object, &obj, &flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
 	struct vm_object *vmo = vm_object_cast(obj);
 	if (!vmo) {
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	return vm_object_read(vmo, dst, offset, count, nr_read);
+	status = vm_object_read(vmo, dst, offset, count, nr_read);
+	put_current_task(self);
+	return status;
 }
 
 kern_status_t sys_vm_object_write(
@@ -73,14 +82,16 @@ kern_status_t sys_vm_object_write(
 	size_t count,
 	size_t *nr_written)
 {
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (!validate_access_r(self, src, count)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
 	if (nr_written
 	    && !validate_access_w(self, nr_written, sizeof *nr_written)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -88,15 +99,19 @@ kern_status_t sys_vm_object_write(
 	handle_flags_t flags = 0;
 	kern_status_t status = task_resolve_handle(self, object, &obj, &flags);
 	if (status != KERN_OK) {
+		put_current_task(self);
 		return status;
 	}
 
 	struct vm_object *vmo = vm_object_cast(obj);
 	if (!vmo) {
+		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	return vm_object_write(vmo, src, offset, count, nr_written);
+	status = vm_object_write(vmo, src, offset, count, nr_written);
+	put_current_task(self);
+	return status;
 }
 
 kern_status_t sys_vm_object_copy(
@@ -114,10 +129,11 @@ kern_status_t sys_vm_object_copy(
 	       src_offset,
 	       count,
 	       nr_copied);
-	struct task *self = current_task();
+	struct task *self = get_current_task();
 
 	if (nr_copied
 	    && !validate_access_w(self, nr_copied, sizeof *nr_copied)) {
+		put_current_task(self);
 		return KERN_MEMORY_FAULT;
 	}
 
@@ -131,16 +147,19 @@ kern_status_t sys_vm_object_copy(
 	status = task_resolve_handle(self, dst, &dst_obj, &dst_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	status = task_resolve_handle(self, src, &src_obj, &src_flags);
 	if (status != KERN_OK) {
 		task_unlock_irqrestore(self, flags);
+		put_current_task(self);
 		return status;
 	}
 
 	task_unlock_irqrestore(self, flags);
+	put_current_task(self);
 
 	struct vm_object *dst_vmo = vm_object_cast(dst_obj);
 	struct vm_object *src_vmo = vm_object_cast(src_obj);

vm/address-space.c

@@ -1261,9 +1261,11 @@ static kern_status_t request_missing_page(
 	/* here:
 	 * `region` is locked.
 	 * `object` is unlocked.
-	 * `irq_flags` must be restored when `region` is unlocked.
-	 * the relevant page in `object` may or may not be committed.
-	 * if it isn't, it needs to be requested.
+	 * `irq_flags` must be restored when `region` is
+	 * unlocked.
+	 * the relevant page in `object` may or may
+	 * not be committed. if it isn't, it needs to be
+	 * requested.
 	 */
 	vm_object_lock(object);
 	address_space_unlock(region);

vm/vm-controller.c

@@ -159,6 +159,7 @@ kern_status_t vm_controller_recv(
 	spin_unlock(&req->req_lock);
 
 	if (req->req_status == PAGE_REQUEST_ASYNC) {
+		put_current_thread(req->req_sender);
 		vm_cache_free(&page_request_cache, req);
 	}
 
@@ -220,7 +221,7 @@ kern_status_t vm_controller_detach_object(
 	req->req_type = PAGE_REQUEST_DETACH;
 	req->req_status = PAGE_REQUEST_ASYNC;
 	req->req_object = vmo->vo_key;
-	req->req_sender = current_thread();
+	req->req_sender = get_current_thread();
 	send_request_async(ctrl, req);
 
 	vmo->vo_ctrl = NULL;
@@ -236,7 +237,7 @@ static void wait_for_reply(
 	unsigned long *lock_flags)
 {
 	struct wait_item waiter;
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 
 	wait_item_init(&waiter, self);
 	for (;;) {
@@ -251,6 +252,7 @@ static void wait_for_reply(
 	}
 
 	self->tr_state = THREAD_READY;
+	put_current_thread(self);
 }
 
 static void fulfill_requests(

vm/vm-object.c

@@ -376,7 +376,7 @@ static kern_status_t request_page(
 	req.req_type = PAGE_REQUEST_READ;
 	req.req_offset = offset;
 	req.req_length = vm_page_order_to_bytes(VM_PAGE_4K);
-	req.req_sender = current_thread();
+	req.req_sender = get_current_thread();
 
 	object_ref(&vo->vo_base);
 	req.req_object = vo->vo_key;
@@ -388,6 +388,7 @@ static kern_status_t request_page(
 	kern_status_t status
 		= vm_controller_send_request(ctrl, &req, irq_flags);
 
+	put_current_thread(req.req_sender);
 	spin_unlock(&req.req_lock);
 	vm_controller_unlock_irqrestore(ctrl, *irq_flags);
 	object_unref(&vo->vo_base);