[SPARC64] mm: update get_user_insn comment

Update comment on get_user_insn to the more general "pte lock", which may
or may not be the page_table_lock.  Note vmtruncate handled like kswapd.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc64/mm/fault.c

@@ -109,7 +109,7 @@ static void bad_kernel_pc(struct pt_regs *regs)
  * this. Additionally, to prevent kswapd from ripping ptes from
  * under us, raise interrupts around the time that we look at the
  * pte, kswapd will have to wait to get his smp ipi response from
- * us. This saves us having to get page_table_lock.
+ * us. vmtruncate likewise. This saves us having to get pte lock.
  */
 static unsigned int get_user_insn(unsigned long tpc)
 {