[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/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;
 }