save cpus.intena in sched(), so we get the right EFLAGS.IF value once a

timer-preempted kernel thread resumes execution in trap() after yield(). otherwise the kernel could get an arbitrary number of nested timer intrs.

save cpus.intena in sched(), so we get the right EFLAGS.IF value once a
228e500a · kolya · 15ce79de · 228e500a
--- a/proc.c
+++ b/proc.c
@@ -207,7 +207,7 @@ scheduler(void)
  c = &cpus[cpu()];
  for(;;){
-    // Enable interrupts on this processor.
+    // Enable interrupts on this processor, in lieu of saving intena.
    sti();
    // Loop over process table looking for process to run.
@@ -240,6 +240,8 @@ scheduler(void)
 void
 sched(void)
 {
+  int intena;
  if(read_eflags()&FL_IF)
    panic("sched interruptible");
  if(cp->state == RUNNING)
@@ -249,7 +251,9 @@ sched(void)
  if(cpus[cpu()].ncli != 1)
    panic("sched locks");
+  intena = cpus[cpu()].intena;
  swtch(&cp->context, &cpus[cpu()].context);
+  cpus[cpu()].intena = intena;
 }
 // Give up the CPU for one scheduling round.