enable interrupts while handling pagefaults -- otherwise TLB shootdown can deadlock

e576fba8 · Nickolai Zeldovich · 6e31b597 · e576fba8
--- a/trap.cc
+++ b/trap.cc
@@ -119,6 +119,7 @@ trap(struct trapframe *tf)

    if(tf->trapno == T_PGFLT){
      uptr addr = rcr2();
+      sti();
      if(addr < USERTOP && pagefault(myproc()->vmap, addr, tf->err) >= 0){
 #if MTRACE
        mtstop(myproc());
@@ -127,6 +128,7 @@ trap(struct trapframe *tf)
 #endif
        return;
      }
+      cli();
    }

    // In user space, assume process misbehaved.