first flush pending LAPIC interrupt and then read the tlbflush value,

to avoid lost tlbflush IPIs.

first flush pending LAPIC interrupt and then read the tlbflush value,
c841ea25 · Nickolai Zeldovich · 69f0e679 · c841ea25
--- a/kernel/trap.cc
+++ b/kernel/trap.cc
@@ -127,8 +127,8 @@ trap(struct trapframe *tf)
    lapiceoi();
    break;
  case T_TLBFLUSH: {
-    u64 nreq = tlbflush_req.load();
    lapiceoi();
+    u64 nreq = tlbflush_req.load();
    lcr3(rcr3());
    mycpu()->tlbflush_done = nreq;
    break;