cvs add spinlock.h

fix race in schedule()

cvs add spinlock.h
66432474 · rtm · 4e8f237b · 66432474 · 66432474 · 66432474
--- a/Notes
+++ b/Notes
@@ -126,3 +126,10 @@ in general, the table locks protect both free-ness and
 why can't i get a lock in console code?
  always triple fault
 lock code shouldn't call cprintf...
+ide_init doesn't work now?
+and IOAPIC: read from unsupported address
+  when running pre-empt user test
+  so maybe something wrong with clock interrupts
+  no! if one cpu holds lock w/ curproc0=,
+    then another cpu can take it, it looks like
+    a recursive acquire()
--- a/proc.c
+++ b/proc.c
@@ -148,7 +148,6 @@ scheduler(void)
    if(i < NPROC){
      np->state = RUNNING;
-      release(&proc_table_lock);
      break;
    }
@@ -159,6 +158,8 @@ scheduler(void)
  cpus[cpu()].lastproc = np;
  curproc[cpu()] = np;
+  release(&proc_table_lock);
  // h/w sets busy bit in TSS descriptor sometimes, and faults
  // if it's set in LTR. so clear tss descriptor busy bit.
  np->gdt[SEG_TSS].sd_type = STS_T32A;

--- a/spinlock.h
+++ b/spinlock.h
+struct spinlock {
+  unsigned int locked;
+  struct proc *p;
+  int count;
+  unsigned locker_pc;
+};
--- a/usertests.c
+++ b/usertests.c
@@ -93,8 +93,8 @@ preempt()
 main()
 {
  puts("usertests starting\n");
-  pipe1();
+  //pipe1();
-  //preempt();
+  preempt();
  while(1)
    ;