From f2d2ab867e30ee530fdeb72c51e7af0302b48e64 Mon Sep 17 00:00:00 2001
From: Jack Halford <jack@0x5.be>
Date: Sun, 15 Dec 2019 12:46:09 +0100
Subject: [PATCH] Step 5: lock/unlock scheduler

---
 src/arch/x86/constants.zig |  1 -
 src/arch/x86/index.zig     |  2 +-
 src/console.zig            |  1 +
 src/constants.zig          |  1 +
 src/index.zig              |  1 +
 src/main.zig               |  5 ++++-
 src/task.zig               | 34 +++++++++++++++++++++++++++-------
 src/vga.zig                |  2 ++
 8 files changed, 37 insertions(+), 10 deletions(-)
 delete mode 100644 src/arch/x86/constants.zig
 create mode 100644 src/constants.zig

diff --git a/src/arch/x86/constants.zig b/src/arch/x86/constants.zig
deleted file mode 100644
index 326ed83..0000000
--- a/src/arch/x86/constants.zig
+++ /dev/null
@@ -1 +0,0 @@
-pub const PAGE_SIZE: usize = 4096;
diff --git a/src/arch/x86/index.zig b/src/arch/x86/index.zig
index 8cd1c39..46de2f3 100644
--- a/src/arch/x86/index.zig
+++ b/src/arch/x86/index.zig
@@ -6,10 +6,10 @@ pub const assert = std.debug.assert;
 pub const kernel = @import("../../index.zig");
 
 // x86 namespace
+pub const PAGE_SIZE: usize = 4096;
 pub usingnamespace @import("lib/io.zig");
 pub usingnamespace @import("lib/instructions.zig");
 pub usingnamespace @import("main.zig");
-pub usingnamespace @import("constants.zig");
 pub const pmem = @import("pmem.zig");
 pub const paging = @import("paging.zig");
 pub const idt = @import("idt.zig");
diff --git a/src/console.zig b/src/console.zig
index 13e9e91..4aac2ec 100644
--- a/src/console.zig
+++ b/src/console.zig
@@ -58,6 +58,7 @@ pub fn loop() void {
             keypress(input_ring_buffer[input_read_index]);
             input_read_index +%= 1;
         }
+        task.lock_scheduler();
         task.schedule();
     }
 }
diff --git a/src/constants.zig b/src/constants.zig
new file mode 100644
index 0000000..b823fb3
--- /dev/null
+++ b/src/constants.zig
@@ -0,0 +1 @@
+pub const SMP: bool = false;
diff --git a/src/index.zig b/src/index.zig
index 5ef7a58..398bdc5 100644
--- a/src/index.zig
+++ b/src/index.zig
@@ -8,6 +8,7 @@ pub usingnamespace @import("vga.zig");
 pub const x86 = @import("arch/x86/index.zig");
 
 ///core
+pub const constants = @import("constants.zig");
 pub const layout = @import("layout.zig");
 pub const multiboot = @import("multiboot.zig");
 pub const vmem = @import("vmem.zig");
diff --git a/src/main.zig b/src/main.zig
index 0145594..a12d1c2 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -28,5 +28,8 @@ export fn kmain(magic: u32, info: *const multiboot.MultibootInfo) noreturn {
     task.new(@ptrToInt(topbar)) catch unreachable;
     task.new(@ptrToInt(console.loop)) catch unreachable;
 
-    while (true) task.schedule();
+    while (true) {
+        task.lock_scheduler();
+        task.schedule();
+    }
 }
diff --git a/src/task.zig b/src/task.zig
index fcce7de..4989336 100644
--- a/src/task.zig
+++ b/src/task.zig
@@ -49,10 +49,10 @@ pub const Task = struct {
 
         // allocate a new stack
         t.esp = (try vmem.malloc(STACK_SIZE)) + STACK_SIZE;
-        // top of stack is the address that ret will pop
+        // this will be what ret goes to
         t.esp -= 4;
         @intToPtr(*usize, t.esp).* = entrypoint;
-        // top of stack is ebp that we will pop
+        // this will be popped into ebp
         t.esp -= 4;
         @intToPtr(*usize, t.esp).* = t.esp + 8;
 
@@ -74,17 +74,18 @@ pub fn new(entrypoint: usize) !void {
 pub fn switch_to(new_task: *ListOfTasks.Node) void {
     assert(new_task.data != current_task.data);
 
+    // save old stack
+    const old_task_esp_addr = &current_task.data.esp;
+
     // switch states
     current_task.data.state = .ReadyToRun;
     new_task.data.state = .Running;
-
-    // save old stack
-    const old_task_esp_addr = &current_task.data.esp;
     current_task = new_task;
-    // x86.cli();
+
+    unlock_scheduler();
+
     // don't inline the asm function, it needs to ret
     @noInlineCall(switch_tasks, new_task.data.esp, @ptrToInt(old_task_esp_addr));
-    // x86.sti();
 }
 
 // circular next
@@ -106,6 +107,25 @@ pub fn schedule() void {
     if (first_ready_to_run()) |t| switch_to(t);
 }
 
+var IRQ_disable_counter: usize = 0;
+
+pub fn lock_scheduler() void {
+    if (constants.SMP == false) {
+        x86.cli();
+        IRQ_disable_counter += 1;
+    }
+}
+pub fn unlock_scheduler() void {
+    if (IRQ_disable_counter == 0) {
+        println("trying to unlock here");
+        while (true) asm volatile ("hlt");
+    }
+    if (constants.SMP == false) {
+        IRQ_disable_counter -= 1;
+        if (IRQ_disable_counter == 0) x86.sti();
+    }
+}
+
 pub fn introspect() void {
     update_time_used();
 
diff --git a/src/vga.zig b/src/vga.zig
index 5aee204..4f71f29 100644
--- a/src/vga.zig
+++ b/src/vga.zig
@@ -75,6 +75,8 @@ pub fn topbar() void {
         vga.cursor_enabled = true;
         vga.cursor = cursor;
         vga.background = bg;
+
+        task.lock_scheduler();
         task.schedule();
     }
 }