deadlock: if the caller of tlbflush is holding a spinlock, another

CPU may have interrupts disabled waiting for that spinlock too, and will never acknowledge our tlb flush..

deadlock: if the caller of tlbflush is holding a spinlock, another
8284cf8d · Nickolai Zeldovich · ea058e70 · 8284cf8d
--- a/hwvm.cc
+++ b/hwvm.cc
@@ -219,6 +219,11 @@ tlbflush()
  u64 myreq = tlbflush_req++;

  pushcli();
+  // the caller may not hold any spinlock, because other CPUs might
+  // be spinning waiting for that spinlock, with interrupts disabled,
+  // so we will deadlock waiting for their TLB flush..
+  assert(mycpu()->ncli == 1);
+
  int myid = mycpu()->id;
  lcr3(rcr3());
  popcli();