[SMP] SMP synchronization and scheduling

kernel/boot/debug.c

@@ -6,9 +6,13 @@
 #include <vga.h>
 #include <serial.h>
 #include <registers.h>
+#include <cpu.h>
+
+lock_t debug_lock;
 
 void debug_init()
 {
+  spin_unlock(&debug_lock);
   vga_init();
   serial_init(PORT_COM1);
 }

kernel/boot/kmain.c

@@ -30,25 +30,23 @@ int kmain(uint64_t multiboot_magic, void *multiboot_data)
   pit_init();
 
   process_t *p1 = process_spawn(0);
-  process_t *p2 = process_spawn(p1);
 
   thread_t *t1 = new_thread(thread_function);
-  thread_t *t2 = new_thread(thread_function);
-  thread_t *t3 = new_thread(thread_function);
-
   process_attach(p1, t1);
-  process_attach(p2, t2);
-  process_attach(p1, t3);
-
-  vmm_set_page(p1->P4, 0x10000, pmm_alloc(), PAGE_PRESENT | PAGE_WRITE);
-  vmm_set_page(p2->P4, 0x10000, pmm_alloc(), PAGE_PRESENT | PAGE_WRITE);
-
-  vmm_p4_memcpy(p1->P4, (void *)0x10000, 0, "Hello, 1", 9);
-  vmm_p4_memcpy(p2->P4, (void *)0x10000, 0, "Hello, 2", 9);
 
   scheduler_insert(t1);
-  scheduler_insert(t2);
-  scheduler_insert(t3);
+  t1 = new_thread(thread_function);
+  process_attach(p1, t1);
+  scheduler_insert(t1);
+  t1 = new_thread(thread_function);
+  process_attach(p1, t1);
+  scheduler_insert(t1);
+  t1 = new_thread(thread_function);
+  process_attach(p1, t1);
+  scheduler_insert(t1);
+  t1 = new_thread(thread_function);
+  process_attach(p1, t1);
+  scheduler_insert(t1);
 
   asm("sti");
   debug_info("BOOT COMPLETE\n");

kernel/cpu/cpu.c

@@ -62,7 +62,9 @@ void cpu_init()
   all_ap_started = 1;
 
   vmm_set_page(0, TRAMPOLINE_ADDR, 0, 0);
-  pmm_free(page);
+  // Keep the GDT mapped for now
+  /* vmm_set_page(0, TRAMPOLINE_GDT, 0, 0); */
+  /* pmm_free(page); */
 
   debug_info("CPU - Status\n");
   for(unsigned int i = 0; i < num_cpu; i++)

kernel/cpu/smp.c

@@ -49,5 +49,7 @@ void ap_start()
   while(!all_ap_started);
   cpu_t *cpu = get_cpu();
   debug_ok("STARTED CPU:%x\n", cpu->id);
+  schedule();
+  debug_error("PANIC: SMP - This line should be unreachable\n");
   for(;;)asm("hlt");
 }

kernel/cpu/sync.S

@@ -0,0 +1,16 @@
+.intel_syntax noprefix
+.global spin_lock
+spin_lock:
+  mov rdx, rdi
+  mov rax, 0x0
+  mov rcx, 0x1
+.retry:
+  xor rax, rax
+  lock cmpxchg [rdx], cl
+  jnz .retry
+  ret
+
+.global spin_unlock
+spin_unlock:
+  movq [rdi], 0x0
+  ret

kernel/include/cpu.h

@@ -20,6 +20,7 @@
 #include <gdt.h>
 #include <process.h>
 #include <thread.h>
+#include <scheduler.h>
 
 typedef struct cpu_t
 {
@@ -51,6 +52,7 @@ void ap_init(cpu_t *cpu);
 
 void trampoline();
 void trampoline_GDT();
+
 #endif
 
 

kernel/include/debug.h

@@ -1,9 +1,10 @@
 #pragma once
 #include <string.h>
 #include <int.h>
+#include <sync.h>
 
 #ifndef NDEBUG
-  #define debug(...) debug_printf(__VA_ARGS__)
+  #define debug(...) ({spin_lock(&debug_lock);debug_printf(__VA_ARGS__);spin_unlock(&debug_lock);})
 #else
   #define debug(...) ((void)0)
 #endif
@@ -12,6 +13,8 @@
 #define debug_warning(...) do{debug("[WARNING] ");debug(__VA_ARGS__);}while(0)
 #define debug_error(...) do{debug("[ERROR] ");debug(__VA_ARGS__);}while(0)
 
+extern lock_t debug_lock;
+
 void debug_init();
 void debug_putch(char c);
 void debug_putsn(char *s, size_t n);

kernel/include/process.h

@@ -4,12 +4,14 @@ typedef struct process_st process_t;
 #include <thread.h>
 #include <mem.h>
 #include <cpu.h>
+#include <sync.h>
 
 typedef struct process_st
 {
   uint64_t pid;
   uint64_t state;
   uint64_t status;
+  lock_t lock;
   struct process_st *parent;
   page_table *P4;
   LIST(struct process_st, children);

kernel/include/sync.h

@@ -0,0 +1,6 @@
+#pragma once
+
+typedef uint64_t lock_t;
+
+void spin_lock(lock_t *lock);
+void spin_unlock(lock_t *lock);

kernel/proc/process.c

@@ -2,6 +2,7 @@
 #include <thread.h>
 #include <debug.h>
 #include <scheduler.h>
+#include <sync.h>
 
 uint64_t pid = 1;
 process_t *init_proc = 0;
@@ -20,7 +21,9 @@ process_t *process_spawn(process_t *parent)
 
   if(parent)
   {
+    spin_lock(&parent->lock);
     LIST_APPEND(parent->children, proc, siblings);
+    spin_unlock(&parent->lock);
   }
 
   if(proc->pid == 1)
@@ -31,8 +34,10 @@ process_t *process_spawn(process_t *parent)
 
 void process_attach(process_t *proc, thread_t *th)
 {
+  spin_lock(&proc->lock);
   LIST_APPEND(proc->threads, th, process_threads);
   th->process = proc;
+  spin_unlock(&proc->lock);
 }
 
 void switch_process(process_t *proc)
@@ -60,6 +65,7 @@ void switch_process(process_t *proc)
 
 void process_exit(process_t *proc, uint64_t status)
 {
+  spin_lock(&proc->lock);
   proc->status = status;
   LIST_FOREACH(proc->children, process_t, c, siblings)
   {
@@ -69,6 +75,7 @@ void process_exit(process_t *proc, uint64_t status)
     LIST_APPEND(init_proc->children, c, siblings);
   }
   proc->state = PROC_STATE_ZOMBIE;
+  spin_unlock(&proc->lock);
 }
 
 void process_free(process_t *proc)

kernel/proc/scheduler.c

@@ -3,6 +3,8 @@
 #include <debug.h>
 #include <sse.h>
 #include <apic.h>
+#include <sync.h>
+#include <debug.h>
 
 LIST(thread_t, ready_queue);
 
@@ -11,29 +13,37 @@ thread_t *scheduler_th;
 #define set_last_thread(new) (get_cpu()->last_thread = (new))
 
 int scheduler_started = 0;
+lock_t scheduler_lock = 0;
 
 void scheduler_insert(thread_t *th)
 {
   // Append thread to the ready queue and prepare it for running
+  spin_lock(&scheduler_lock);
   LIST_APPEND(ready_queue, th, ready_queue);
   th->state = THREAD_STATE_READY;
+  spin_unlock(&scheduler_lock);
 }
 
 void scheduler_remove(thread_t *th)
 {
   // Remove thread from the ready queue
+  spin_lock(&scheduler_lock);
   LIST_REMOVE(ready_queue, th, ready_queue);
+  spin_unlock(&scheduler_lock);
 }
 
 thread_t *scheduler_next()
 {
   // Get the next thread from the ready queue
+  spin_lock(&scheduler_lock);
   if(!LIST_EMPTY(ready_queue))
   {
     thread_t *th = LIST_FIRST(ready_queue);
-    scheduler_remove(th);
+    LIST_REMOVE(ready_queue, th, ready_queue);
+    spin_unlock(&scheduler_lock);
     return th;
   }
+  spin_unlock(&scheduler_lock);
   return 0;
 }
 

kernel/proc/thread.c

@@ -8,7 +8,6 @@
 
 uint64_t tid = 1;
 
-
 thread_t *new_thread(void (*func)(void))
 {
   // Set up original stack of thread