Don't kill process when inside kernel.

72fef4f8 · rsc · 4ed974f5 · 72fef4f8
--- a/trap.c
+++ b/trap.c
@@ -70,11 +70,18 @@ trap(struct Trapframe *tf)
    lapic_timerintr();
    if(cpus[cpu()].nlock)
      panic("timer interrupt while holding a lock");
+    if((read_eflags() & FL_IF) == 0)
+      panic("timer interrupt but interrupts now disabled");
    if(cp){
-      if((read_eflags() & FL_IF) == 0)
+      // Force process exit if it has been killed
-        panic("timer interrupt but interrupts now disabled");
+      // and the interrupt came from user space.
-      if(cp->killed)
+      // (If the kernel was executing at time of interrupt,
+      // don't kill the process.  Let the process get back
+      // out to its regular system call return.)
+      if((tf->tf_cs&3) == 3 && cp->killed)
        proc_exit();
+      // Force process to give up CPU and let others run.
      if(cp->state == RUNNING)
        yield();
    }