New scheduler.

Removed cli and sti stack in favor of tracking number of locks held on each CPU and explicit conditionals in spinlock.c.

New scheduler.
65bd8e13 · rsc · 40a2a083 · 65bd8e13 · 65bd8e13 · 65bd8e13
--- a/console.c
+++ b/console.c
@@ -113,7 +113,7 @@ void
 cprintf(char *fmt, ...)
 {
  int i, state = 0, c;
-  unsigned int *ap = (unsigned int *) &fmt + 1;
+  unsigned int *ap = (unsigned int *)(void*)&fmt + 1;
  if(use_console_lock)
    acquire(&console_lock);

--- a/defs.h
+++ b/defs.h
@@ -13,7 +13,6 @@ struct proc;
 struct jmpbuf;
 void setupsegs(struct proc *);
 struct proc * newproc(void);
-void swtch(int);
 struct spinlock;
 void sleep(void *, struct spinlock *);
 void wakeup(void *);
@@ -22,8 +21,6 @@ void proc_exit(void);
 int proc_kill(int);
 int proc_wait(void);
 void yield(void);
-void cli(void);
-void sti(void);
 // swtch.S
 struct jmpbuf;

--- a/dot-bochsrc
+++ b/dot-bochsrc
@@ -107,7 +107,7 @@ romimage: file=$BXSHARE/BIOS-bochs-latest, address=0xf0000
 #  650Mhz Athlon K-7 with Linux 2.4.4/egcs-2.91.66  2 to  2.5 Mips
 #  400Mhz Pentium II with Linux 2.0.36/egcs-1.0.3   1 to  1.8 Mips
 #=======================================================================
-cpu: count=2, ips=10000000
+cpu: count=2, ips=10000000, reset_on_triple_fault=0
 #=======================================================================
 # MEGS

--- a/main.c
+++ b/main.c
@@ -18,19 +18,19 @@ extern uint8_t _binary_userfs_start[], _binary_userfs_size[];
 extern int use_console_lock;
+struct spinlock sillylock;  // hold this to keep interrupts disabled
 int
 main()
 {
  struct proc *p;
  if (acpu) {
-    cpus[cpu()].clis = 1;
    cprintf("an application processor\n");
    idtinit(); // CPU's idt
    lapic_init(cpu());
    lapic_timerinit();
    lapic_enableintr();
-    sti();
    scheduler();
  }
  acpu = 1;
@@ -40,10 +40,9 @@ main()
  mp_init(); // collect info about this machine
+  acquire(&sillylock);
  use_console_lock = 1;
-  cpus[cpu()].clis = 1; // cpu starts as if we had called cli()
  lapic_init(mp_bcpu());
  cprintf("\nxV6\n\n");
@@ -56,7 +55,7 @@ main()
  // create fake process zero
  p = &proc[0];
  memset(p, 0, sizeof *p);
-  p->state = WAITING;
+  p->state = SLEEPING;
  p->sz = 4 * PAGE;
  p->mem = kalloc(p->sz);
  memset(p->mem, 0, p->sz);
@@ -88,6 +87,7 @@ main()
  //load_icode(p, _binary_userfs_start, (unsigned) _binary_userfs_size);
  p->state = RUNNABLE;
  cprintf("loaded userfs\n");
+  release(&sillylock);
  scheduler();

--- a/proc.c
+++ b/proc.c
--- a/proc.h
+++ b/proc.h
@@ -33,7 +33,7 @@ struct jmpbuf {
  int jb_eip;
 };
-enum proc_state { UNUSED, EMBRYO, WAITING, RUNNABLE, RUNNING, ZOMBIE };
+enum proc_state { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
 struct proc{
  char *mem; // start of process's physical memory
@@ -46,7 +46,6 @@ struct proc{
  int ppid;
  void *chan; // sleep
  int killed;
-  int locks; // # of locks currently held
  struct fd *fds[NOFILE];
  struct Taskstate ts;  // only to give cpu address of kernel stack
@@ -71,7 +70,7 @@ struct cpu {
  struct jmpbuf jmpbuf;
  char mpstack[MPSTACK]; // per-cpu start-up stack, only used to get into main()
  struct proc *lastproc;  // last proc scheduled on this cpu (never NULL)
-  int clis; // cli() nesting depth
+  int nlock; // # of locks currently held
 };
 extern struct cpu cpus[NCPU];

--- a/spinlock.c
+++ b/spinlock.c
@@ -6,42 +6,35 @@
 #include "proc.h"
 #include "spinlock.h"
-#define DEBUG 0
+// Can't call cprintf from inside these routines,
+// because cprintf uses them itself.
+#define cprintf dont_use_cprintf
 extern int use_console_lock;
-int getcallerpc(void *v) {
+int
+getcallerpc(void *v)
+{
 	return ((int*)v)[-1];
 }
 void
 acquire1(struct spinlock * lock, struct proc *cp)
 {
-  if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
+	if(cpus[cpu()].nlock++ == 0)
 		cli();
-  while ( cmpxchg(0, 1, &lock->locked) == 1 ) { ; }
+	while(cmpxchg(0, 1, &lock->locked) == 1)
+		;
+	cpuid(0, 0, 0, 0, 0);	// memory barrier
 	lock->locker_pc = getcallerpc(&lock);
-  if(cp)
-    cp->locks += 1;
-  if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu(), getcallerpc(&lock));
 }
 void
 release1(struct spinlock * lock, struct proc *cp)
 {
+	cpuid(0, 0, 0, 0, 0);	// memory barrier
-  if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
+	lock->locked = 0;
+	if(--cpus[cpu()].nlock == 0)
-  if(lock->locked != 1)
-    panic("release");
-  if(cp)
-    cp->locks -= 1;
-  cmpxchg(1, 0, &lock->locked);
 		sti();
 }
@@ -56,3 +49,4 @@ release(struct spinlock *lock)
 {
 	release1(lock, curproc[cpu()]);
 }
--- a/syscall.c
+++ b/syscall.c
@@ -34,8 +34,9 @@ fetchint(struct proc *p, unsigned addr, int *ip)
  return 0;
 }
+// This arg is void* so that both int* and uint* can be passed.
 int
-fetcharg(int argno, int *ip)
+fetcharg(int argno, void *ip)
 {
  unsigned esp;

--- a/trap.c
+++ b/trap.c
@@ -36,11 +36,6 @@ trap(struct Trapframe *tf)
 {
  int v = tf->tf_trapno;
-  if(cpus[cpu()].clis){
-    cprintf("cpu %d v %d eip %x\n", cpu(), v, tf->tf_eip);
-    panic("interrupt while interrupts are off");
-  }
  if(v == T_SYSCALL){
    struct proc *cp = curproc[cpu()];
    int num = cp->tf->tf_regs.reg_eax;
@@ -56,12 +51,10 @@ trap(struct Trapframe *tf)
      panic("trap ret but not RUNNING");
    if(tf != cp->tf)
      panic("trap ret wrong tf");
-    if(cp->locks){
+    if(cpus[cpu()].nlock){
      cprintf("num=%d\n", num);
      panic("syscall returning locks held");
    }
-    if(cpus[cpu()].clis)
-      panic("syscall returning but clis != 0");
    if((read_eflags() & FL_IF) == 0)
      panic("syscall returning but FL_IF clear");
    if(read_esp() < (unsigned)cp->kstack ||
@@ -75,7 +68,7 @@ trap(struct Trapframe *tf)
  if(v == (IRQ_OFFSET + IRQ_TIMER)){
    struct proc *cp = curproc[cpu()];
    lapic_timerintr();
-    if(cp && cp->locks)
+    if(cpus[cpu()].nlock)
      panic("timer interrupt while holding a lock");
    if(cp){
 #if 1

--- a/trapasm.S
+++ b/trapasm.S
 #include "mmu.h"
 	.text
-        .globl alltraps
+.globl trap
-        .globl trap
+.globl trapret1
+.globl alltraps
 alltraps:
        /* vectors.S sends all traps here */
        pushl   %ds     # build
@@ -16,11 +18,11 @@ alltraps:
        addl $4, %esp
        # return falls through to trapret...
-        .globl trapret
 	/*
         * a forked process RETs here
         * expects ESP to point to a Trapframe
         */
+.globl trapret
 trapret:
        popal
        popl %es
@@ -28,6 +30,10 @@ trapret:
        addl $0x8, %esp /* trapno and errcode */
        iret
+.globl forkret
+forkret:
+	call forkret1
+	jmp trapret
 .globl 	acpu
 acpu:

--- a/x86.h
+++ b/x86.h
@@ -29,6 +29,8 @@ static __inline uint32_t read_ebp(void) __attribute__((always_inline));
 static __inline uint32_t read_esp(void) __attribute__((always_inline));
 static __inline void cpuid(uint32_t info, uint32_t *eaxp, uint32_t *ebxp, uint32_t *ecxp, uint32_t *edxp);
 static __inline uint64_t read_tsc(void) __attribute__((always_inline));
+static __inline void cli(void) __attribute__((always_inline));
+static __inline void sti(void) __attribute__((always_inline));
 static __inline void
 breakpoint(void)
@@ -304,6 +306,18 @@ read_tsc(void)
        return tsc;
 }
+static __inline void
+cli(void)
+{
+	__asm__ volatile("cli");
+}
+static __inline void
+sti(void)
+{
+	__asm__ volatile("sti");
+}
 struct PushRegs {
    /* registers as pushed by pusha */
    uint32_t reg_edi;