[PATCH] mm: powerpc ptlock comments
Update comments (only) on page_table_lock and mmap_sem in arch/powerpc.
Removed the comment on page_table_lock from hash_huge_page: since it's no
longer taking page_table_lock itself, it's irrelevant whether others are; but
how it is safe (even against huge file truncation?) I can't say.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 426c269..9250f14 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -754,9 +754,7 @@
}
/*
- * No need to use ldarx/stdcx here because all who
- * might be updating the pte will hold the
- * page_table_lock
+ * No need to use ldarx/stdcx here
*/
*ptep = __pte(new_pte & ~_PAGE_BUSY);
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 4bd7b0a..ed6ed2e 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -495,7 +495,7 @@
* We use it to preload an HPTE into the hash table corresponding to
* the updated linux PTE.
*
- * This must always be called with the mm->page_table_lock held
+ * This must always be called with the pte lock held.
*/
void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
pte_t pte)
diff --git a/arch/powerpc/mm/tlb_32.c b/arch/powerpc/mm/tlb_32.c
index 6c3dc3c..ad580f3 100644
--- a/arch/powerpc/mm/tlb_32.c
+++ b/arch/powerpc/mm/tlb_32.c
@@ -149,6 +149,12 @@
return;
}
+ /*
+ * It is safe to go down the mm's list of vmas when called
+ * from dup_mmap, holding mmap_sem. It would also be safe from
+ * unmap_region or exit_mmap, but not from vmtruncate on SMP -
+ * but it seems dup_mmap is the only SMP case which gets here.
+ */
for (mp = mm->mmap; mp != NULL; mp = mp->vm_next)
flush_range(mp->vm_mm, mp->vm_start, mp->vm_end);
FINISH_FLUSH;
diff --git a/arch/powerpc/mm/tlb_64.c b/arch/powerpc/mm/tlb_64.c
index 53e31b8..859d29a 100644
--- a/arch/powerpc/mm/tlb_64.c
+++ b/arch/powerpc/mm/tlb_64.c
@@ -95,7 +95,7 @@
void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf)
{
- /* This is safe as we are holding page_table_lock */
+ /* This is safe since tlb_gather_mmu has disabled preemption */
cpumask_t local_cpumask = cpumask_of_cpu(smp_processor_id());
struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
@@ -206,7 +206,7 @@
void pte_free_finish(void)
{
- /* This is safe as we are holding page_table_lock */
+ /* This is safe since tlb_gather_mmu has disabled preemption */
struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
if (*batchp == NULL)
