CRIS v32: Avoid work when switching between tasks with shared memory descriptors in mm/tlb.c

There is no need to do all this work if they share memory descriptors.
Also, fix some minor whitespace and long lines.

arch/cris/arch-v32/mm/tlb.c

@@ -30,8 +30,8 @@ do {						\
  * The TLB can host up to 256 different mm contexts at the same time. The running
  * context is found in the PID register. Each TLB entry contains a page_id that
  * has to match the PID register to give a hit. page_id_map keeps track of which
- * mm is assigned to which page_id, making sure it's known when to invalidate TLB
- * entries.
+ * mm's is assigned to which page_id's, making sure it's known when to
+ * invalidate TLB entries.
  *
  * The last page_id is never running, it is used as an invalid page_id so that
  * it's possible to make TLB entries that will nerver match.
@@ -179,6 +179,7 @@ void
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
+	if (prev != next) {
 		int cpu = smp_processor_id();
 
 		/* Make sure there is a MMU context. */
@@ -188,20 +189,19 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 		spin_unlock(&mmu_context_lock);
 
 		/*
-	 * Remember the pgd for the fault handlers. Keep a separate copy of it
-	 * because current and active_mm might be invalid at points where
-	 * there's still a need to derefer the pgd.
+		 * Remember the pgd for the fault handlers. Keep a seperate
+		 * copy of it because current and active_mm might be invalid
+		 * at points where * there's still a need to derefer the pgd.
 		 */
 		per_cpu(current_pgd, cpu) = next->pgd;
 
 		/* Switch context in the MMU. */
-        if (tsk && task_thread_info(tsk))
-        {
-          SPEC_REG_WR(SPEC_REG_PID, next->context.page_id | task_thread_info(tsk)->tls);
-        }
-        else
-        {
+		if (tsk && task_thread_info(tsk)) {
+			SPEC_REG_WR(SPEC_REG_PID, next->context.page_id |
+				task_thread_info(tsk)->tls);
+		} else {
 			SPEC_REG_WR(SPEC_REG_PID, next->context.page_id);
 		}
+	}
 }