3 files changed, 24 insertions, 3 deletions

diff --git a/include/asm-alpha/barrier.h b/include/asm-alpha/barrier.h
index 384dc08d6f53..ac78eba909bc 100644
--- a/include/asm-alpha/barrier.h
+++ b/include/asm-alpha/barrier.h
@@ -24,7 +24,7 @@ __asm__ __volatile__("mb": : :"memory")
 #define smp_mb()        barrier()
 #define smp_rmb()       barrier()
 #define smp_wmb()       barrier()
-#define smp_read_barrier_depends()      barrier()
+#define smp_read_barrier_depends()      do { } while (0)
 #endif
 
 #define set_mb(var, value) \
diff --git a/include/asm-alpha/param.h b/include/asm-alpha/param.h
index 0982f1d39499..e691ecfedb2c 100644
--- a/include/asm-alpha/param.h
+++ b/include/asm-alpha/param.h
@@ -5,8 +5,12 @@
    hardware ignores reprogramming.  We also need userland buy-in to the 
    change in HZ, since this is visible in the wait4 resources etc.  */
 
+#ifdef __KERNEL__
 #define HZ              CONFIG_HZ
 #define USER_HZ         HZ
+#else
+#define HZ              1024
+#endif
 
 #define EXEC_PAGESIZE   8192
 
diff --git a/include/asm-alpha/pgtable.h b/include/asm-alpha/pgtable.h
index 05ce5fba43e3..3f0c59f6d8aa 100644
--- a/include/asm-alpha/pgtable.h
+++ b/include/asm-alpha/pgtable.h
@@ -287,17 +287,34 @@ extern inline pte_t pte_mkspecial(pte_t pte)	{ return pte; }
 #define pgd_index(address)      (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
 #define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address))
 
+/*
+ * The smp_read_barrier_depends() in the following functions are required to
+ * order the load of *dir (the pointer in the top level page table) with any
+ * subsequent load of the returned pmd_t *ret (ret is data dependent on *dir).
+ *
+ * If this ordering is not enforced, the CPU might load an older value of
+ * *ret, which may be uninitialized data. See mm/memory.c:__pte_alloc for
+ * more details.
+ *
+ * Note that we never change the mm->pgd pointer after the task is running, so
+ * pgd_offset does not require such a barrier.
+ */
+
 /* Find an entry in the second-level page table.. */
 extern inline pmd_t * pmd_offset(pgd_t * dir, unsigned long address)
 {
-        return (pmd_t *) pgd_page_vaddr(*dir) + ((address >> PMD_SHIFT) & (PTRS_PER_PAGE - 1));
+        pmd_t *ret = (pmd_t *) pgd_page_vaddr(*dir) + ((address >> PMD_SHIFT) & (PTRS_PER_PAGE - 1));
+        smp_read_barrier_depends(); /* see above */
+        return ret;
 }
 
 /* Find an entry in the third-level page table.. */
 extern inline pte_t * pte_offset_kernel(pmd_t * dir, unsigned long address)
 {
-        return (pte_t *) pmd_page_vaddr(*dir)
+        pte_t *ret = (pte_t *) pmd_page_vaddr(*dir)
                 + ((address >> PAGE_SHIFT) & (PTRS_PER_PAGE - 1));
+        smp_read_barrier_depends(); /* see above */
+        return ret;
 }
 
 #define pte_offset_map(dir,addr)        pte_offset_kernel((dir),(addr))