Bugfixed MP scheduling code in MP build
[tpg/acess2.git] / Kernel / arch / x86 / proc.c
index 9ad06a5..bee311a 100644 (file)
@@ -3,7 +3,9 @@
  * proc.c
  */
 #include <acess.h>
+#include <threads.h>
 #include <proc.h>
+#include <desctab.h>
 #include <mm_virt.h>
 #include <errno.h>
 #if USE_MP
 
 // === CONSTANTS ===
 #define        SWITCH_MAGIC    0xFFFACE55      // There is no code in this area
-#define TIMER_DIVISOR  11931   //~100Hz
+// Base is 1193182
+#define TIMER_BASE      1193182
+#define TIMER_DIVISOR   11931  //~100Hz
+
+// === TYPES ===
+#if USE_MP
+typedef struct sCPU
+{
+       Uint8   APICID;
+       Uint8   State;  // 0: Unavaliable, 1: Idle, 2: Active
+       Uint16  Resvd;
+       tThread *Current;
+       tThread *IdleThread;
+}      tCPU;
+#endif
 
 // === IMPORTS ===
 extern tGDT    gGDT[];
-extern void APStartup();       // 16-bit AP startup code
-extern Uint    GetEIP();       // start.asm
+extern tIDT    gIDT[];
+extern void APWait(void);      // 16-bit AP pause code
+extern void APStartup(void);   // 16-bit AP startup code
+extern Uint    GetEIP(void);   // start.asm
+extern int     GetCPUNum(void);        // start.asm
 extern Uint32  gaInitPageDir[1024];    // start.asm
 extern void    Kernel_Stack_Top;
-extern volatile int    giThreadListLock;
+extern tSpinlock       glThreadListLock;
 extern int     giNumCPUs;
 extern int     giNextTID;
 extern int     giTotalTickets;
@@ -32,52 +51,63 @@ extern tThread      gThreadZero;
 extern tThread *gActiveThreads;
 extern tThread *gSleepingThreads;
 extern tThread *gDeleteThreads;
-extern tThread *Threads_GetNextToRun(int CPU);
-extern void    Threads_Dump();
+extern void    Threads_Dump(void);
 extern tThread *Threads_CloneTCB(Uint *Err, Uint Flags);
-extern void    Isr7();
+extern void    Isr8(void);     // Double Fault
+extern void    Proc_ReturnToUser(void);
 
 // === PROTOTYPES ===
-void   ArchThreads_Init();
+void   ArchThreads_Init(void);
 #if USE_MP
 void   MP_StartAP(int CPU);
 void   MP_SendIPI(Uint8 APICID, int Vector, int DeliveryMode);
 #endif
-void   Proc_Start();
-tThread        *Proc_GetCurThread();
-void   Proc_ChangeStack();
+void   Proc_Start(void);
+tThread        *Proc_GetCurThread(void);
+void   Proc_ChangeStack(void);
  int   Proc_Clone(Uint *Err, Uint Flags);
-void   Proc_Scheduler();
+void   Proc_StartProcess(Uint16 SS, Uint Stack, Uint Flags, Uint16 CS, Uint IP);
+void   Proc_CallFaultHandler(tThread *Thread);
+void   Proc_Scheduler(int CPU);
 
 // === GLOBALS ===
 // --- Multiprocessing ---
 #if USE_MP
+volatile int   giNumInitingCPUs = 0;
 tMPInfo        *gMPFloatPtr = NULL;
+volatile Uint32        giMP_TimerCount;        // Start Count for Local APIC Timer
 tAPIC  *gpMP_LocalAPIC = NULL;
 Uint8  gaAPIC_to_CPU[256] = {0};
 tCPU   gaCPUs[MAX_CPUS];
+tTSS   gaTSSs[MAX_CPUS];       // TSS Array
+ int   giProc_BootProcessorID = 0;
 #else
 tThread        *gCurrentThread = NULL;
 #endif
 #if USE_PAE
 Uint32 *gPML4s[4] = NULL;
 #endif
-tTSS   *gTSSs = NULL;
+tTSS   *gTSSs = NULL;  // Pointer to TSS array
 tTSS   gTSS0 = {0};
 // --- Error Recovery ---
-char   gaDoubleFaultStack[1024];
+char   gaDoubleFaultStack[1024] __attribute__ ((section(".padata")));
 tTSS   gDoubleFault_TSS = {
-       .ESP0 = (Uint)&gaDoubleFaultStack[1023],
+       .ESP0 = (Uint)&gaDoubleFaultStack[1024],
        .SS0 = 0x10,
-       .EIP = (Uint)Isr7
+       .CR3 = (Uint)gaInitPageDir - KERNEL_BASE,
+       .EIP = (Uint)Isr8,
+       .ESP = (Uint)&gaDoubleFaultStack[1024],
+       .CS = 0x08,     .SS = 0x10,
+       .DS = 0x10,     .ES = 0x10,
+       .FS = 0x10,     .GS = 0x10,
 };
 
 // === CODE ===
 /**
- * \fn void ArchThreads_Init()
+ * \fn void ArchThreads_Init(void)
  * \brief Starts the process scheduler
  */
-void ArchThreads_Init()
+void ArchThreads_Init(void)
 {
        Uint    pos = 0;
        
@@ -157,7 +187,7 @@ void ArchThreads_Init()
                Log("\t.ExtendedTableChecksum = 0x%02x", mptable->ExtendedTableChecksum);
                Log("}");
                
-               gpMP_LocalAPIC = (void*)MM_MapHWPage(mptable->LocalAPICMemMap, 1);
+               gpMP_LocalAPIC = (void*)MM_MapHWPages(mptable->LocalAPICMemMap, 1);
                
                ents = mptable->Entries;
                giNumCPUs = 0;
@@ -194,18 +224,19 @@ void ArchThreads_Init()
                                gaCPUs[giNumCPUs].State = 0;
                                giNumCPUs ++;
                                
-                               // Send IPI
-                               if( !(ents->Proc.CPUFlags & 2) )
-                               {
-                                       MP_StartAP( giNumCPUs-1 );
+                               // Set BSP Variable
+                               if( ents->Proc.CPUFlags & 2 ) {
+                                       giProc_BootProcessorID = giNumCPUs-1;
                                }
                                
                                break;
+                       
+                       #if DUMP_MP_TABLES
                        case 1: // Bus
                                entSize = 8;
                                Log("%i: Bus", i);
                                Log("\t.ID = %i", ents->Bus.ID);
-                               Log("\t.TypeString = '%6c'", ents->Bus.TypeString);
+                               Log("\t.TypeString = '%6C'", ents->Bus.TypeString);
                                break;
                        case 2: // I/O APIC
                                entSize = 8;
@@ -238,15 +269,16 @@ void ArchThreads_Init()
                        default:
                                Log("%i: Unknown (%i)", i, ents->Type);
                                break;
+                       #endif
                        }
                        ents = (void*)( (Uint)ents + entSize );
                }
                
                if( giNumCPUs > MAX_CPUS ) {
                        Warning("Too many CPUs detected (%i), only using %i of them", giNumCPUs, MAX_CPUS);
+                       giNumCPUs = MAX_CPUS;
                }
-               
-               Panic("Uh oh... MP Table Parsing is unimplemented\n");
+               gTSSs = gaTSSs;
        }
        else {
                Log("No MP Table was found, assuming uniprocessor\n");
@@ -256,20 +288,48 @@ void ArchThreads_Init()
        #else
        giNumCPUs = 1;
        gTSSs = &gTSS0;
+       MM_FinishVirtualInit();
        #endif
        
+       #if 0
        // Initialise Double Fault TSS
-       /*
-       gGDT[5].LimitLow = sizeof(tTSS);
-       gGDT[5].LimitHi = 0;
-       gGDT[5].Access = 0x89;  // Type
-       gGDT[5].Flags = 0x4;
-       */
        gGDT[5].BaseLow = (Uint)&gDoubleFault_TSS & 0xFFFF;
        gGDT[5].BaseMid = (Uint)&gDoubleFault_TSS >> 16;
        gGDT[5].BaseHi = (Uint)&gDoubleFault_TSS >> 24;
        
+       // Set double fault IDT to use the new TSS
+       gIDT[8].OffsetLo = 0;
+       gIDT[8].CS = 5<<3;
+       gIDT[8].Flags = 0x8500;
+       gIDT[8].OffsetHi = 0;
+       #endif
+       
+       // Set timer frequency
+       outb(0x43, 0x34);       // Set Channel 0, Low/High, Rate Generator
+       outb(0x40, TIMER_DIVISOR&0xFF); // Low Byte of Divisor
+       outb(0x40, (TIMER_DIVISOR>>8)&0xFF);    // High Byte
+       
        #if USE_MP
+       // Get the count setting for APIC timer
+       Log("Determining APIC Count");
+       __asm__ __volatile__ ("sti");
+       while( giMP_TimerCount == 0 )   __asm__ __volatile__ ("hlt");
+       __asm__ __volatile__ ("cli");
+       Log("APIC Count %i", giMP_TimerCount);
+       {
+               Uint64  freq = giMP_TimerCount;
+               freq /= TIMER_DIVISOR;
+               freq *= TIMER_BASE;
+               if( (freq /= 1000) < 2*1000)
+                       Log("Bus Frequency %i KHz", freq);
+               else if( (freq /= 1000) < 2*1000)
+                       Log("Bus Frequency %i MHz", freq);
+               else if( (freq /= 1000) < 2*1000)
+                       Log("Bus Frequency %i GHz", freq);
+               else
+                       Log("Bus Frequency %i THz", freq);
+       }
+       
        // Initialise Normal TSS(s)
        for(pos=0;pos<giNumCPUs;pos++)
        {
@@ -283,18 +343,17 @@ void ArchThreads_Init()
                gGDT[6+pos].BaseHi = ((Uint)(&gTSSs[pos])) >> 24;
        #if USE_MP
        }
-       for(pos=0;pos<giNumCPUs;pos++) {
-       #endif
-               __asm__ __volatile__ ("ltr %%ax"::"a"(0x30+pos*8));
-       #if USE_MP
-       }
        #endif
        
+       // Load the BSP's TSS
+       __asm__ __volatile__ ("ltr %%ax"::"a"(0x30));
+       
        #if USE_MP
        gaCPUs[0].Current = &gThreadZero;
        #else
        gCurrentThread = &gThreadZero;
        #endif
+       gThreadZero.CurCPU = 0;
        
        #if USE_PAE
        gThreadZero.MemState.PDP[0] = 0;
@@ -304,11 +363,6 @@ void ArchThreads_Init()
        gThreadZero.MemState.CR3 = (Uint)gaInitPageDir - KERNEL_BASE;
        #endif
        
-       // Set timer frequency
-       outb(0x43, 0x34);       // Set Channel 0, Low/High, Rate Generator
-       outb(0x40, TIMER_DIVISOR&0xFF); // Low Byte of Divisor
-       outb(0x40, (TIMER_DIVISOR>>8)&0xFF);    // High Byte
-       
        // Create Per-Process Data Block
        MM_Allocate(MM_PPD_CFG);
        
@@ -320,57 +374,127 @@ void ArchThreads_Init()
 void MP_StartAP(int CPU)
 {
        Log("Starting AP %i (APIC %i)", CPU, gaCPUs[CPU].APICID);
+       
        // Set location of AP startup code and mark for a warm restart
-       *(Uint16*)(KERNEL_BASE|0x467) = (Uint)&APStartup - (KERNEL_BASE|0xFFFF0);
+       *(Uint16*)(KERNEL_BASE|0x467) = (Uint)&APWait - (KERNEL_BASE|0xFFFF0);
        *(Uint16*)(KERNEL_BASE|0x469) = 0xFFFF;
        outb(0x70, 0x0F);       outb(0x71, 0x0A);       // Warm Reset
-       MP_SendIPI(gaCPUs[CPU].APICID, 0, 5);
+       MP_SendIPI(gaCPUs[CPU].APICID, 0, 5);   // Init IPI
+       
+       // Delay
+       inb(0x80); inb(0x80); inb(0x80); inb(0x80);
+       
+       // TODO: Use a better address, preferably registered with the MM
+       // - MM_AllocDMA mabye?
+       // Create a far jump
+       *(Uint8*)(KERNEL_BASE|0x11000) = 0xEA;  // Far JMP
+       *(Uint16*)(KERNEL_BASE|0x11001) = (Uint)&APStartup - (KERNEL_BASE|0xFFFF0);     // IP
+       *(Uint16*)(KERNEL_BASE|0x11003) = 0xFFFF;       // CS
+       // Send a Startup-IPI to make the CPU execute at 0x11000 (which we
+       // just filled)
+       MP_SendIPI(gaCPUs[CPU].APICID, 0x11, 6);        // StartupIPI
+       
+       giNumInitingCPUs ++;
 }
 
+/**
+ * \brief Send an Inter-Processor Interrupt
+ * \param APICID       Processor's Local APIC ID
+ * \param Vector       Argument of some kind
+ * \param DeliveryMode Type of signal?
+ */
 void MP_SendIPI(Uint8 APICID, int Vector, int DeliveryMode)
 {
-       Uint32  addr = (Uint)gpMP_LocalAPIC + 0x300;
        Uint32  val;
        
        // Hi
        val = (Uint)APICID << 24;
-       Log("*%p = 0x%08x", addr+0x10, val);
-       *(Uint32*)(addr+0x10) = val;
+       Log("*%p = 0x%08x", &gpMP_LocalAPIC->ICR[1], val);
+       gpMP_LocalAPIC->ICR[1].Val = val;
        // Low (and send)
        val = ((DeliveryMode & 7) << 8) | (Vector & 0xFF);
-       Log("*%p = 0x%08x", addr, val);
-       *(Uint32*)addr = val;
+       Log("*%p = 0x%08x", &gpMP_LocalAPIC->ICR[0], val);
+       gpMP_LocalAPIC->ICR[0].Val = val;
 }
 #endif
 
 /**
- * \fn void Proc_Start()
+ * \fn void Proc_Start(void)
  * \brief Start process scheduler
  */
-void Proc_Start()
+void Proc_Start(void)
 {
+       #if USE_MP
+        int    i;
+       #endif
+       
+       #if USE_MP
+       // Start APs
+       for( i = 0; i < giNumCPUs; i ++ )
+       {
+               // Create Idle Task
+               if(Proc_Clone(0, 0) == 0)
+               {
+                       gaCPUs[i].IdleThread = Proc_GetCurThread();
+                       gaCPUs[i].IdleThread->ThreadName = "Idle Thread";
+                       gaCPUs[i].IdleThread->NumTickets = 0;   // Never called randomly
+                       gaCPUs[i].IdleThread->Quantum = 1;      // 1 slice quantum
+                       for(;;) HALT(); // Just yeilds
+               }
+               gaCPUs[i].Current = NULL;
+               
+               // Start the AP
+               if( i != giProc_BootProcessorID ) {
+                       MP_StartAP( i );
+               }
+       }
+       
+       // BSP still should run the current task
+       gaCPUs[0].Current = &gThreadZero;
+       
+       // Start interrupts and wait for APs to come up
+       Log("Waiting for APs to come up\n");
+       __asm__ __volatile__ ("sti");
+       while( giNumInitingCPUs )       __asm__ __volatile__ ("hlt");
+       MM_FinishVirtualInit();
+       #else
+       // Create Idle Task
+       if(Proc_Clone(0, 0) == 0)
+       {
+               tThread *cur = Proc_GetCurThread();
+               cur->ThreadName = "Idle Thread";
+               Threads_SetTickets(0);  // Never called randomly
+               cur->Quantum = 1;       // 1 slice quantum
+               for(;;) HALT(); // Just yeilds
+       }
+       
+       // Set current task
+       gCurrentThread = &gThreadZero;
+       
        // Start Interrupts (and hence scheduler)
        __asm__ __volatile__("sti");
+       #endif
 }
 
 /**
- * \fn tThread *Proc_GetCurThread()
+ * \fn tThread *Proc_GetCurThread(void)
  * \brief Gets the current thread
  */
-tThread *Proc_GetCurThread()
+tThread *Proc_GetCurThread(void)
 {
        #if USE_MP
-       return gaCPUs[ gaAPIC_to_CPU[gpMP_LocalAPIC->ID.Val&0xFF] ].Current;
+       //return gaCPUs[ gaAPIC_to_CPU[gpMP_LocalAPIC->ID.Val&0xFF] ].Current;
+       return gaCPUs[ GetCPUNum() ].Current;
        #else
        return gCurrentThread;
        #endif
 }
 
 /**
- * \fn void Proc_ChangeStack()
+ * \fn void Proc_ChangeStack(void)
  * \brief Swaps the current stack for a new one (in the proper stack reigon)
  */
-void Proc_ChangeStack()
+void Proc_ChangeStack(void)
 {
        Uint    esp, ebp;
        Uint    tmpEbp, oldEsp;
@@ -475,6 +599,7 @@ int Proc_Clone(Uint *Err, Uint Flags)
        eip = GetEIP();
        if(eip == SWITCH_MAGIC) {
                outb(0x20, 0x20);       // ACK Timer and return as child
+               __asm__ __volatile__ ("sti");   // Restart interrupts
                return 0;
        }
        
@@ -488,10 +613,10 @@ int Proc_Clone(Uint *Err, Uint Flags)
 }
 
 /**
- * \fn int Proc_SpawnWorker()
+ * \fn int Proc_SpawnWorker(void)
  * \brief Spawns a new worker thread
  */
-int Proc_SpawnWorker()
+int Proc_SpawnWorker(void)
 {
        tThread *new, *cur;
        Uint    eip, esp, ebp;
@@ -536,10 +661,10 @@ int Proc_SpawnWorker()
 }
 
 /**
- * \fn Uint Proc_MakeUserStack()
+ * \fn Uint Proc_MakeUserStack(void)
  * \brief Creates a new user stack
  */
-Uint Proc_MakeUserStack()
+Uint Proc_MakeUserStack(void)
 {
         int    i;
        Uint    base = USER_STACK_TOP - USER_STACK_SZ;
@@ -552,13 +677,12 @@ Uint Proc_MakeUserStack()
        if(i != -1)     return 0;
        
        // Allocate Stack - Allocate incrementally to clean up MM_Dump output
-       for( i = 0; i < USER_STACK_SZ/4069; i++ )
+       for( i = 0; i < USER_STACK_SZ/0x1000; i++ )
                MM_Allocate( base + (i<<12) );
        
        return base + USER_STACK_SZ;
 }
 
-
 /**
  * \fn void Proc_StartUser(Uint Entrypoint, Uint *Bases, int ArgC, char **ArgV, char **EnvP, int DataSize)
  * \brief Starts a user task
@@ -570,19 +694,30 @@ void Proc_StartUser(Uint Entrypoint, Uint *Bases, int ArgC, char **ArgV, char **
        Uint    delta;
        Uint16  ss, cs;
        
-       LOG("stack = 0x%x", stack);
+       //Log("stack = %p", stack);
        
        // Copy Arguments
-       stack = (void*)( (Uint)stack - DataSize );
+       stack -= DataSize/sizeof(*stack);
        memcpy( stack, ArgV, DataSize );
        
-       // Adjust Arguments and environment
-       delta = (Uint)stack - (Uint)ArgV;
-       ArgV = (char**)stack;
-       for( i = 0; ArgV[i]; i++ )      ArgV[i] += delta;
-       i ++;
-       EnvP = &ArgV[i];
-       for( i = 0; EnvP[i]; i++ )      EnvP[i] += delta;
+       //Log("stack = %p", stack);
+       
+       if( DataSize )
+       {
+               // Adjust Arguments and environment
+               delta = (Uint)stack - (Uint)ArgV;
+               ArgV = (char**)stack;
+               for( i = 0; ArgV[i]; i++ )
+                       ArgV[i] += delta;
+               i ++;
+               
+               // Do we care about EnvP?
+               if( EnvP ) {
+                       EnvP = &ArgV[i];
+                       for( i = 0; EnvP[i]; i++ )
+                               EnvP[i] += delta;
+               }
+       }
        
        // User Mode Segments
        ss = 0x23;      cs = 0x1B;
@@ -594,13 +729,18 @@ void Proc_StartUser(Uint Entrypoint, Uint *Bases, int ArgC, char **ArgV, char **
        while(*Bases)
                *--stack = *Bases++;
        *--stack = 0;   // Return Address
-       delta = (Uint)stack;    // Reuse delta to save SP
        
-       *--stack = ss;          //Stack Segment
-       *--stack = delta;       //Stack Pointer
-       *--stack = 0x0202;      //EFLAGS (Resvd (0x2) and IF (0x20))
-       *--stack = cs;          //Code Segment
-       *--stack = Entrypoint;  //EIP
+       Proc_StartProcess(ss, (Uint)stack, 0x202, cs, Entrypoint);
+}
+
+void Proc_StartProcess(Uint16 SS, Uint Stack, Uint Flags, Uint16 CS, Uint IP)
+{
+       Uint    *stack = (void*)Stack;
+       *--stack = SS;          //Stack Segment
+       *--stack = Stack;       //Stack Pointer
+       *--stack = Flags;       //EFLAGS (Resvd (0x2) and IF (0x20))
+       *--stack = CS;          //Code Segment
+       *--stack = IP;  //EIP
        //PUSHAD
        *--stack = 0xAAAAAAAA;  // eax
        *--stack = 0xCCCCCCCC;  // ecx
@@ -611,10 +751,10 @@ void Proc_StartUser(Uint Entrypoint, Uint *Bases, int ArgC, char **ArgV, char **
        *--stack = 0x51515151;  // esi
        *--stack = 0xB4B4B4B4;  // ebp
        //Individual PUSHs
-       *--stack = ss;  // ds
-       *--stack = ss;  // es
-       *--stack = ss;  // fs
-       *--stack = ss;  // gs
+       *--stack = SS;  // ds
+       *--stack = SS;  // es
+       *--stack = SS;  // fs
+       *--stack = SS;  // gs
        
        __asm__ __volatile__ (
        "mov %%eax,%%esp;\n\t"  // Set stack pointer
@@ -661,6 +801,18 @@ int Proc_Demote(Uint *Err, int Dest, tRegs *Regs)
        return 0;
 }
 
+/**
+ * \brief Calls a signal handler in user mode
+ * \note Used for signals
+ */
+void Proc_CallFaultHandler(tThread *Thread)
+{
+       // Rewinds the stack and calls the user function
+       // Never returns
+       __asm__ __volatile__ ("mov %0, %%ebp;\n\tcall Proc_ReturnToUser" :: "r"(Thread->FaultHandler));
+       for(;;);
+}
+
 /**
  * \fn void Proc_Scheduler(int CPU)
  * \brief Swap current thread and clears dead threads
@@ -671,7 +823,7 @@ void Proc_Scheduler(int CPU)
        tThread *thread;
        
        // If the spinlock is set, let it complete
-       if(giThreadListLock)    return;
+       if(IS_LOCKED(&glThreadListLock))        return;
        
        // Clear Delete Queue
        while(gDeleteThreads)
@@ -686,7 +838,15 @@ void Proc_Scheduler(int CPU)
        
        // Check if there is any tasks running
        if(giNumActiveThreads == 0) {
+               #if 0
                Log("No Active threads, sleeping");
+               #endif
+               #if USE_MP
+               if(CPU)
+                       gpMP_LocalAPIC->EOI.Val = 0;
+               else
+               #endif
+                       outb(0x20, 0x20);
                __asm__ __volatile__ ("hlt");
                return;
        }
@@ -698,29 +858,33 @@ void Proc_Scheduler(int CPU)
        thread = gCurrentThread;
        #endif
        
-       // Reduce remaining quantum and continue timeslice if non-zero
-       if(thread->Remaining--) return;
-       // Reset quantum for next call
-       thread->Remaining = thread->Quantum;
-       
-       // Get machine state
-       __asm__ __volatile__ ("mov %%esp, %0":"=r"(esp));
-       __asm__ __volatile__ ("mov %%ebp, %0":"=r"(ebp));
-       eip = GetEIP();
-       if(eip == SWITCH_MAGIC) return; // Check if a switch happened
-       
-       // Save machine state
-       thread->SavedState.ESP = esp;
-       thread->SavedState.EBP = ebp;
-       thread->SavedState.EIP = eip;
+       if( thread )
+       {
+               // Reduce remaining quantum and continue timeslice if non-zero
+               if(thread->Remaining--) return;
+               // Reset quantum for next call
+               thread->Remaining = thread->Quantum;
+               
+               // Get machine state
+               __asm__ __volatile__ ("mov %%esp, %0":"=r"(esp));
+               __asm__ __volatile__ ("mov %%ebp, %0":"=r"(ebp));
+               eip = GetEIP();
+               if(eip == SWITCH_MAGIC) return; // Check if a switch happened
+               
+               // Save machine state
+               thread->SavedState.ESP = esp;
+               thread->SavedState.EBP = ebp;
+               thread->SavedState.EIP = eip;
+       }
        
-       // Get next thread
-       thread = Threads_GetNextToRun(CPU);
+       // Get next thread to run
+       thread = Threads_GetNextToRun(CPU, thread);
        
-       // Error Check
+       // No avaliable tasks, just go into low power mode
        if(thread == NULL) {
-               Warning("Hmm... Threads_GetNextToRun returned NULL, I don't think this should happen.\n");
-               return;
+               //HALT();
+               //return;
+               thread = gaCPUs[CPU].IdleThread;
        }
        
        #if DEBUG_TRACE_SWITCH
@@ -738,8 +902,10 @@ void Proc_Scheduler(int CPU)
        gCurrentThread = thread;
        #endif
        
+       //Log("CPU = %i", CPU);
+       
        // Update Kernel Stack pointer
-       gTSSs[CPU].ESP0 = thread->KernelStack;
+       gTSSs[CPU].ESP0 = thread->KernelStack-4;
        
        // Set address space
        #if USE_PAE
@@ -747,6 +913,14 @@ void Proc_Scheduler(int CPU)
        #else
                __asm__ __volatile__ ("mov %0, %%cr3"::"a"(thread->MemState.CR3));
        #endif
+       
+       #if 0
+       if(thread->SavedState.ESP > 0xC0000000
+       && thread->SavedState.ESP < thread->KernelStack-0x2000) {
+               Log_Warning("Proc", "Possible bad ESP %p (PID %i)", thread->SavedState.ESP);
+       }
+       #endif
+       
        // Switch threads
        __asm__ __volatile__ (
                "mov %1, %%esp\n\t"     // Restore ESP

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