[kernel] Have thread call scheduler on blocking

Instead of making every callsite that may make a thread do a blocking
operation also invoke the scheduler, move that logic into thread
implementation - if the thread is blocking and is the current thread,
call schedule().

Related changes in this commit:

- Also make exiting threads and processes call the scheduler when
  blocking.
- Threads start blocked, and get automatically added to the scheduler's
  blocked list.

src/kernel/objects/endpoint.cpp

@@ -1,7 +1,6 @@
 #include "objects/endpoint.h"
 #include "objects/process.h"
 #include "objects/thread.h"
-#include "scheduler.h"
 #include "vm_space.h"
 
 endpoint::endpoint() :
@@ -25,16 +24,13 @@ endpoint::close()
 j6_status_t
 endpoint::send(size_t len, void *data)
 {
-	scheduler &s = scheduler::get();
+	thread_data sender = { &thread::current(), data };
-	TCB *tcb = s.current();
-	thread_data sender = { thread::from_tcb(tcb), data };
 	sender.len = len;
 
 	if (!check_signal(j6_signal_endpoint_can_send)) {
 		assert_signal(j6_signal_endpoint_can_recv);
-		sender.th->wait_on_object(this);
 		m_blocked.append(sender);
-		s.schedule();
+		sender.th->wait_on_object(this);
 
 		// we woke up having already finished the send
 		// because it happened in the receiver
@@ -54,16 +50,13 @@ endpoint::send(size_t len, void *data)
 j6_status_t
 endpoint::receive(size_t *len, void *data)
 {
-	scheduler &s = scheduler::get();
+	thread_data receiver = { &thread::current(), data };
-	TCB *tcb = s.current();
-	thread_data receiver = { thread::from_tcb(tcb), data };
 	receiver.len_p = len;
 
 	if (!check_signal(j6_signal_endpoint_can_recv)) {
 		assert_signal(j6_signal_endpoint_can_send);
-		receiver.th->wait_on_object(this);
 		m_blocked.append(receiver);
-		s.schedule();
+		receiver.th->wait_on_object(this);
 
 		// we woke up having already finished the recv
 		// because it happened in the sender

src/kernel/objects/process.cpp

@@ -5,6 +5,7 @@
 #include "objects/process.h"
 #include "objects/thread.h"
 #include "objects/vm_area.h"
+#include "scheduler.h"
 
 // This object is initialized _before_ global constructors are called,
 // so we don't want it to have a global constructor at all, lest it
@@ -62,6 +63,9 @@ process::exit(unsigned code)
 	}
 	m_return_code = code;
 	assert_signal(j6_signal_process_exit);
+
+	if (this == bsp_cpu_data.p)
+		scheduler::get().schedule();
 }
 
 void
@@ -90,6 +94,9 @@ process::update()
 thread *
 process::create_thread(uint8_t priority, bool user)
 {
+	if (priority == default_pri)
+		priority = scheduler::default_priority;
+
 	thread *th = new thread(*this, priority);
 	kassert(th, "Failed to create thread!");
 
@@ -104,6 +111,7 @@ process::create_thread(uint8_t priority, bool user)
 	}
 
 	m_threads.append(th);
+	scheduler::get().add_thread(th->tcb());
 	return th;
 }
 

src/kernel/objects/process.h

@@ -18,6 +18,9 @@ public:
 	/// Size of userspace thread stacks
 	constexpr static size_t stack_size = 0x4000;
 
+	/// Value that represents default priority
+	constexpr static uint8_t default_pri = 0xff;
+
 	/// Constructor.
 	process();
 
@@ -43,7 +46,7 @@ public:
 	/// \args priority  The new thread's scheduling priority
 	/// \args user      If true, create a userspace stack for this thread
 	/// \returns        The newly created thread object
-	thread * create_thread(uint8_t priorty, bool user = true);
+	thread * create_thread(uint8_t priorty = default_pri, bool user = true);
 
 	/// Start tracking an object with a handle.
 	/// \args obj  The object this handle refers to

src/kernel/objects/thread.cpp

@@ -26,8 +26,6 @@ thread::thread(process &parent, uint8_t pri, uintptr_t rsp0) :
 		setup_kernel_stack();
 	else
 		m_tcb.rsp0 = rsp0;
-
-	set_state(state::ready);
 }
 
 thread::~thread()
@@ -49,12 +47,16 @@ thread::current()
 	return *bsp_cpu_data.t;
 }
 
+inline void schedule_if_current(thread *t) { if (t == bsp_cpu_data.t) scheduler::get().schedule(); }
+
 void
 thread::wait_on_signals(kobject *obj, j6_signal_t signals)
 {
 	m_wait_type = wait_type::signal;
 	m_wait_data = signals;
 	clear_state(state::ready);
+
+	schedule_if_current(this);
 }
 
 void
@@ -63,6 +65,8 @@ thread::wait_on_time(uint64_t t)
 	m_wait_type = wait_type::time;
 	m_wait_data = t;
 	clear_state(state::ready);
+
+	schedule_if_current(this);
 }
 
 void
@@ -71,6 +75,8 @@ thread::wait_on_object(kobject *o)
 	m_wait_type = wait_type::object;
 	m_wait_data = reinterpret_cast<uint64_t>(o);
 	clear_state(state::ready);
+
+	schedule_if_current(this);
 }
 
 bool
@@ -134,6 +140,8 @@ thread::exit(uint32_t code)
 	set_state(state::exited);
 	clear_state(state::ready);
 	assert_signal(j6_signal_thread_exit);
+
+	schedule_if_current(this);
 }
 
 void
@@ -200,7 +208,8 @@ thread *
 thread::create_idle_thread(process &kernel, uint8_t pri, uintptr_t rsp0)
 {
 	thread *idle = new thread(kernel, pri, rsp0);
-	idle->set_state(thread::state::constant);
+	idle->set_state(state::constant);
+	idle->set_state(state::ready);
 	log::info(logs::task, "Created idle thread as koid %llx", idle->koid());
 
 	return idle;

src/kernel/scheduler.cpp

@@ -141,13 +141,14 @@ scheduler::create_process(bool user)
 {
 	process *p = new process;
 	thread *th = p->create_thread(default_priority, user);
-	auto *tcb = th->tcb();
 
+	auto *tcb = th->tcb();
 	tcb->time_left = quantum(default_priority);
 
 	log::debug(logs::task, "Creating thread %llx, priority %d, time slice %d",
 			th->koid(), tcb->priority, tcb->time_left);
 
+	th->set_state(thread::state::ready);
 	return th;
 }
 
@@ -183,8 +184,6 @@ scheduler::load_process(const char *name, const void *data, size_t size)
 
 	tcb->rsp3 = process::stacks_top;
 
-	m_runlists[default_priority].push_back(tcb);
-
 	log::debug(logs::task, "Loading thread %s: koid %llx  pri %d", name, th->koid(), tcb->priority);
 	log::debug(logs::task, "     RSP  %016lx", tcb->rsp);
 	log::debug(logs::task, "     RSP0 %016lx", tcb->rsp0);
@@ -203,7 +202,7 @@ scheduler::create_kernel_task(void (*task)(), uint8_t priority, bool constant)
 	if (constant)
 		th->set_state(thread::state::constant);
 
-	m_runlists[priority].push_back(tcb);
+	th->set_state(thread::state::ready);
 
 	log::debug(logs::task, "Creating kernel task: thread %llx  pri %d", th->koid(), tcb->priority);
 	log::debug(logs::task, "    RSP0 %016lx", tcb->rsp0);
@@ -247,7 +246,6 @@ void scheduler::prune(uint64_t now)
 		if (!exited && !ready)
 			continue;
 
-
 		if (exited) {
 			// If the current thread has exited, wait until the next call
 			// to prune() to delete it, because we may be deleting our current

src/kernel/scheduler.h

@@ -69,7 +69,7 @@ public:
 	/// \returns  A pointer to the current thread's TCB
 	inline TCB * current() { return m_current; }
 
-	inline void add_thread(TCB *t) { m_runlists[t->priority].push_back(static_cast<tcb_node*>(t)); }
+	inline void add_thread(TCB *t) { m_blocked.push_back(static_cast<tcb_node*>(t)); }
 
 	/// Get a reference to the system scheduler
 	/// \returns  A reference to the global system scheduler

src/kernel/syscalls/object.cpp

@@ -5,14 +5,12 @@
 #include "log.h"
 #include "objects/process.h"
 #include "objects/thread.h"
-#include "scheduler.h"
 
 namespace syscalls {
 
 j6_status_t
 object_wait(j6_handle_t handle, j6_signal_t mask, j6_signal_t *sigs)
 {
-	scheduler &s = scheduler::get();
 	thread &th = thread::current();
 	process &p = process::current();
 
@@ -28,7 +26,6 @@ object_wait(j6_handle_t handle, j6_signal_t mask, j6_signal_t *sigs)
 
 	obj->add_blocked_thread(&th);
 	th.wait_on_signals(obj, mask);
-	s.schedule();
 
 	j6_status_t result = th.get_wait_result();
 	if (result == j6_status_ok) {

src/kernel/syscalls/process.cpp

@@ -3,7 +3,6 @@
 
 #include "log.h"
 #include "objects/process.h"
-#include "scheduler.h"
 
 namespace syscalls {
 
@@ -20,13 +19,10 @@ process_koid(j6_koid_t *koid)
 j6_status_t
 process_exit(int64_t status)
 {
-	auto &s = scheduler::get();
 	process &p = process::current();
-
 	log::debug(logs::syscall, "Process %llx exiting with code %d", p.koid(), status);
 
 	p.exit(status);
-	s.schedule();
 
 	log::error(logs::syscall, "returned to exit syscall");
 	return j6_err_unexpected;

src/kernel/syscalls/thread.cpp

@@ -4,7 +4,6 @@
 #include "log.h"
 #include "objects/process.h"
 #include "objects/thread.h"
-#include "scheduler.h"
 
 namespace syscalls {
 
@@ -21,14 +20,14 @@ thread_koid(j6_koid_t *koid)
 j6_status_t
 thread_create(void *rip, j6_handle_t *handle)
 {
-	scheduler &s = scheduler::get();
 	thread &parent = thread::current();
 	process &p = parent.parent();
 
-	thread *child = p.create_thread(scheduler::default_priority);
+	thread *child = p.create_thread();
 	child->add_thunk_user(reinterpret_cast<uintptr_t>(rip));
 	*handle = p.add_handle(child);
-	s.add_thread(child->tcb());
+	child->clear_state(thread::state::loading);
+	child->set_state(thread::state::ready);
 
 	log::debug(logs::syscall, "Thread %llx spawned new thread %llx, handle %d",
 		parent.koid(), child->koid(), *handle);
@@ -39,11 +38,9 @@ thread_create(void *rip, j6_handle_t *handle)
 j6_status_t
 thread_exit(int64_t status)
 {
-	auto &s = scheduler::get();
 	thread &th = thread::current();
 	log::debug(logs::syscall, "Thread %llx exiting with code %d", th.koid(), status);
 	th.exit(status);
-	s.schedule();
 
 	log::error(logs::syscall, "returned to exit syscall");
 	return j6_err_unexpected;
@@ -52,22 +49,18 @@ thread_exit(int64_t status)
 j6_status_t
 thread_pause()
 {
-	auto &s = scheduler::get();
 	thread &th = thread::current();
 	th.wait_on_signals(&th, -1ull);
-	s.schedule();
 	return j6_status_ok;
 }
 
 j6_status_t
 thread_sleep(uint64_t til)
 {
-	auto &s = scheduler::get();
 	thread &th = thread::current();
 	log::debug(logs::syscall, "Thread %llx sleeping until %llu", th.koid(), til);
 
 	th.wait_on_time(til);
-	s.schedule();
 	return j6_status_ok;
 }