CRIS v32: Avoid work when switching between tasks with shared memory descriptors...
Jesper Nilsson [Fri, 25 Jan 2008 17:08:07 +0000 (18:08 +0100)]
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

index a076ef6..eda5ebc 100644 (file)
@@ -13,8 +13,8 @@
 #include <asm/arch/hwregs/supp_reg.h>
 
 #define UPDATE_TLB_SEL_IDX(val)                                        \
-do {                                                           \
-       unsigned long tlb_sel;                                  \
+do {                                                           \
+       unsigned long tlb_sel;                                  \
                                                                \
        tlb_sel = REG_FIELD(mmu, rw_mm_tlb_sel, idx, val);      \
        SUPP_REG_WR(RW_MM_TLB_SEL, tlb_sel);                    \
@@ -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.
@@ -179,29 +179,29 @@ void
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
          struct task_struct *tsk)
 {
-       int cpu = smp_processor_id();
-
-       /* Make sure there is a MMU context. */
-       spin_lock(&mmu_context_lock);
-       get_mmu_context(next);
-       cpu_set(cpu, next->cpu_vm_mask);
-       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.
-        */
-       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
-        {
-          SPEC_REG_WR(SPEC_REG_PID, next->context.page_id);
-        }
+       if (prev != next) {
+               int cpu = smp_processor_id();
+
+               /* Make sure there is a MMU context. */
+               spin_lock(&mmu_context_lock);
+               get_mmu_context(next);
+               cpu_set(cpu, next->cpu_vm_mask);
+               spin_unlock(&mmu_context_lock);
+
+               /*
+                * 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 {
+                       SPEC_REG_WR(SPEC_REG_PID, next->context.page_id);
+               }
+       }
 }