Initial process waiting/waking

Processes can now wait on signals/children/time. There is no clock
currently so "time" is just a monotonically increating tick count. Added
a SLEEP syscall to test this waiting/waking.

src/drivers/nulldrv/main.s

@@ -2,6 +2,7 @@ global _start
 _start:
 	xor rbp, rbp	; Sentinel rbp
 	mov r11, 0		; counter
+	mov rbx, 20		; sleep timeout
 
 .loop:
 	mov rax, 1		; DEBUG syscall
@@ -10,13 +11,15 @@ _start:
 	int 0xee
 
 	inc r11
-	cmp r11, 3
+	cmp r11, 2
 
 	jle .loop
 
-	mov rax, 3		; PAUSE syscall
+	mov rax, 4		; SLEEP syscall
 	; syscall
 	int 0xee
 
+	add rbx, 20
+
 	mov r11, 0
 	jmp .loop

src/kernel/process.cpp

@@ -0,0 +1,64 @@
+#include "process.h"
+
+
+void
+process::wait_on_signal(uint64_t sigmask)
+{
+	waiting = process_wait::signal;
+	waiting_info = sigmask;
+	flags -= process_flags::ready;
+}
+
+void
+process::wait_on_child(uint32_t pid)
+{
+	waiting = process_wait::child;
+	waiting_info = pid;
+	flags -= process_flags::ready;
+}
+
+void
+process::wait_on_time(uint64_t time)
+{
+	waiting = process_wait::time;
+	waiting_info = time;
+	flags -= process_flags::ready;
+}
+
+bool
+process::wake_on_signal(int signal)
+{
+	if (waiting != process_wait::signal ||
+		(waiting_info & (1 << signal)) == 0)
+		return false;
+
+	waiting = process_wait::none;
+	flags += process_flags::ready;
+	return true;
+}
+
+bool
+process::wake_on_child(process *child)
+{
+	if (waiting != process_wait::child ||
+		(waiting_info && waiting_info != child->pid))
+		return false;
+
+	waiting = process_wait::none;
+	flags += process_flags::ready;
+	return true;
+}
+
+
+bool
+process::wake_on_time(uint64_t now)
+{
+	if (waiting != process_wait::time ||
+		waiting_info > now)
+		return false;
+
+	waiting = process_wait::none;
+	flags += process_flags::ready;
+	return true;
+}
+

src/kernel/process.h

@@ -0,0 +1,81 @@
+#pragma once
+/// \file process.h
+/// The processes and related definitions
+#include "kutil/enum_bitfields.h"
+#include "kutil/linked_list.h"
+#include "kutil/memory.h"
+#include "page_manager.h"
+
+
+enum class process_flags : uint32_t
+{
+	running   = 0x00000001,
+	ready     = 0x00000002,
+	loading   = 0x00000004,
+
+	const_pri = 0x80000000,
+
+	none      = 0x00000000
+};
+IS_BITFIELD(process_flags);
+
+enum class process_wait : uint8_t
+{
+	none,
+	signal,
+	child,
+	time
+};
+
+/// A process
+struct process
+{
+	uint32_t pid;
+	uint32_t ppid;
+
+	process_flags flags;
+
+	uint16_t reserved0;
+
+	uint8_t priority;
+
+	process_wait waiting;
+	uint64_t waiting_info;
+
+	uint32_t return_code;
+
+	uint32_t reserved1;
+
+	addr_t rsp;
+	page_table *pml4;
+
+	/// Unready this process until it gets a signal
+	/// \arg sigmask  A bitfield of signals to wake on
+	void wait_on_signal(uint64_t sigmask);
+
+	/// Unready this process until a child exits
+	/// \arg pid  PID of the child to wait for, or 0 for any
+	void wait_on_child(uint32_t pid);
+
+	/// Unready this process until after the given time
+	/// \arg time  The time after which to wake
+	void wait_on_time(uint64_t time);
+
+	/// If this process is waiting on the given signal, wake it
+	/// \argument signal  The signal sent to the process
+	/// \returns  True if this wake was handled
+	bool wake_on_signal(int signal);
+
+	/// If this process is waiting on the given child, wake it
+	/// \argument child  The process that exited
+	/// \returns  True if this wake was handled
+	bool wake_on_child(process *child);
+
+	/// If this process is waiting on a time, check it
+	/// \argument now  The current time
+	/// \returns  True if this wake was handled
+	bool wake_on_time(uint64_t now);
+};
+
+using process_list = kutil::linked_list<process>;
+using process_node = process_list::item_type;

src/kernel/scheduler.cpp

@@ -40,6 +40,7 @@ scheduler::scheduler(lapic *apic) :
 	idle->rsp = 0; // This will get set when we switch away
 	idle->pml4 = page_manager::get_pml4();
 	idle->flags =
+		process_flags::running |
 		process_flags::ready |
 		process_flags::const_pri;
 
@@ -156,6 +157,7 @@ scheduler::create_process(const char *name, const void *data, size_t size)
 	proc->rsp = reinterpret_cast<addr_t>(loader_state);
 	proc->pml4 = pml4;
 	proc->flags =
+		process_flags::running |
 		process_flags::ready |
 		process_flags::loading;
 
@@ -175,9 +177,65 @@ scheduler::start()
 	m_apic->enable_timer(isr::isrTimer, 128, quantum, false);
 }
 
+void scheduler::prune(uint64_t now)
+{
+	// Find processes that aren't ready or aren't running and
+	// move them to the appropriate lists.
+	for (auto &pri_list : m_runlists) {
+		auto *proc = pri_list.front();
+		while (proc) {
+			bool running = proc->flags && process_flags::running;
+			bool ready = proc->flags && process_flags::ready;
+			if (running && ready) {
+				proc = proc->next();
+				continue;
+			}
+
+			auto *remove = proc;
+			proc = proc->next();
+			pri_list.remove(remove);
+
+			if (!(remove->flags && process_flags::running)) {
+				auto *parent = get_process_by_id(remove->ppid);
+				if (parent && parent->wake_on_child(remove)) {
+					m_blocked.remove(parent);
+					m_runlists[parent->priority].push_front(parent);
+					m_process_allocator.push(remove);
+				} else {
+					m_exited.push_back(remove);
+				}
+			} else {
+				m_blocked.push_back(remove);
+			}
+		}
+	}
+
+	// Find blocked processes that are ready (possibly after waking wating
+	// ones) and move them to the appropriate runlist.
+	auto *proc = m_blocked.front();
+	while (proc) {
+		bool ready = proc->flags && process_flags::ready;
+		ready |= proc->wake_on_time(now);
+		if (!ready) {
+			proc = proc->next();
+			continue;
+		}
+
+		auto *remove = proc;
+		proc = proc->next();
+		m_blocked.remove(remove);
+		m_runlists[remove->priority].push_front(remove);
+	}
+}
+
 addr_t
 scheduler::schedule(addr_t rsp0)
 {
+
+	// TODO: lol a real clock
+	static uint64_t now = 0;
+	prune(++now);
+
 	m_current->rsp = rsp0;
 	m_runlists[m_current->priority].remove(m_current);
 
@@ -198,7 +256,6 @@ scheduler::schedule(addr_t rsp0)
 	// Set rsp0 to after the end of the about-to-be-popped cpu state
 	tss_set_stack(0, rsp0 + sizeof(cpu_state));
 	wrmsr(msr::ia32_kernel_gs_base, rsp0);
-	log::debug(logs::task, "Scheduler set kernel_gs_base to %016lx", rsp0);
 
 	// Swap page tables
 	page_table *pml4 = m_current->pml4;
@@ -220,3 +277,24 @@ scheduler::tick(addr_t rsp0)
 	m_apic->reset_timer(quantum);
 	return rsp0;
 }
+
+process_node *
+scheduler::get_process_by_id(uint32_t pid)
+{
+	// TODO: this needs to be a hash map
+	for (auto *proc : m_blocked) {
+		if (proc->pid == pid) return proc;
+	}
+
+	for (int i = 0; i < num_priorities; ++i) {
+		for (auto *proc : m_runlists[i]) {
+			if (proc->pid == pid) return proc;
+		}
+	}
+
+	for (auto *proc : m_exited) {
+		if (proc->pid == pid) return proc;
+	}
+
+	return nullptr;
+}

src/kernel/scheduler.h

@@ -1,11 +1,9 @@
 #pragma once
 /// \file scheduler.h
 /// The task scheduler and related definitions
-#include "kutil/enum_bitfields.h"
-#include "kutil/linked_list.h"
 #include "kutil/memory.h"
 #include "kutil/slab_allocator.h"
-#include "kutil/vector.h"
+#include "process.h"
 
 class lapic;
 struct page_table;
@@ -13,42 +11,6 @@ struct cpu_state;
 
 extern "C" addr_t isr_handler(addr_t, cpu_state);
 
-enum class process_flags : uint32_t
-{
-	running   = 0x00000001,
-	ready     = 0x00000002,
-	loading   = 0x00000004,
-
-	const_pri = 0x80000000,
-
-	none      = 0x00000000
-};
-IS_BITFIELD(process_flags);
-
-/// A process
-struct process
-{
-	uint32_t pid;
-	uint32_t ppid;
-
-	uint8_t priority;
-
-	uint8_t reserved0;
-	uint16_t reserved;
-
-	process_flags flags;
-
-	addr_t rsp;
-	page_table *pml4;
-
-	/// Helper to check if this process is ready
-	/// \returns  true if the process has the ready flag
-	inline bool ready() { return bitfield_has(flags, process_flags::ready); }
-};
-
-using process_list = kutil::linked_list<process>;
-using process_node = process_list::item_type;
-using process_slab = kutil::slab_allocator<process>;
 
 /// The task scheduler
 class scheduler
@@ -80,10 +42,17 @@ public:
 	/// \returns  A pointer to the current process' process struct
 	inline process * current() { return m_current; }
 
+	/// Look up a process by its PID
+	/// \arg pid  The requested PID
+	/// \returns  The process matching that PID, or nullptr
+	process_node * get_process_by_id(uint32_t pid);
+
 	/// Get a reference to the system scheduler
 	/// \returns  A reference to the global system scheduler
 	static scheduler & get() { return s_instance; }
 
+private:
+	friend addr_t syscall_dispatch(addr_t, const cpu_state &);
 	friend addr_t isr_handler(addr_t, cpu_state);
 
 	/// Handle a timer tick
@@ -91,15 +60,19 @@ public:
 	/// \returns   The stack pointer to switch to
 	addr_t tick(addr_t rsp0);
 
-private:
+	void prune(uint64_t now);
+
 	lapic *m_apic;
 
 	uint32_t m_next_pid;
 
-	process_node *m_current;
+	using process_slab = kutil::slab_allocator<process>;
 	process_slab m_process_allocator;
+
+	process_node *m_current;
 	process_list m_runlists[num_priorities];
 	process_list m_blocked;
+	process_list m_exited;
 
 	static scheduler s_instance;
 };

src/kernel/syscall.cpp

@@ -2,6 +2,7 @@
 #include "cpu.h"
 #include "debug.h"
 #include "msr.h"
+#include "process.h"
 #include "scheduler.h"
 #include "syscall.h"
 
@@ -62,12 +63,22 @@ syscall_dispatch(addr_t return_rsp, const cpu_state &regs)
 
 			auto &s = scheduler::get();
 			auto *p = s.current();
-			p->flags -= process_flags::ready;
+			p->wait_on_signal(-1ull);
-			//log::debug(logs::task, "Pausing process %d, flags: %08x", p->pid, p->flags);
 			cons->printf("\nReceived PAUSE syscall\n");
 			return_rsp = s.tick(return_rsp);
-			//log::debug(logs::task, "Switching to stack %016lx", return_rsp);
+			cons->set_color();
-			cons->printf("\nDONE WITH PAUSE syscall\n");
+		}
+		break;
+
+	case syscall::sleep:
+		{
+			cons->set_color(11);
+
+			auto &s = scheduler::get();
+			auto *p = s.current();
+			p->wait_on_time(regs.rbx);
+			cons->printf("\nReceived SLEEP syscall\n");
+			return_rsp = s.tick(return_rsp);
 			cons->set_color();
 		}
 		break;

src/kernel/syscall.h

@@ -11,6 +11,7 @@ enum class syscall : uint64_t
 	debug,
 	message,
 	pause,
+	sleep,
 
 	last_syscall
 };