From c74df32c724a1652ad8399b4891bb02c9d43743a Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 29 Oct 2005 18:16:23 -0700 Subject: [PATCH] mm: ptd_alloc take ptlock Second step in pushing down the page_table_lock. Remove the temporary bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not to hold page_table_lock, whether it's on init_mm or a user mm; take page_table_lock internally to check if a racing task already allocated. Convert their callers from common code. But avoid coming back to change them again later: instead of moving the spin_lock(&mm->page_table_lock) down, switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which encapsulate the mapping+locking and unlocking+unmapping together, and in the end may use alternatives to the mm page_table_lock itself. These callers all hold mmap_sem (some exclusively, some not), so at no level can a page table be whipped away from beneath them; and pte_alloc uses the "atomic" pmd_present to test whether it needs to allocate. It appears that on all arches we can safely descend without page_table_lock. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/fork.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'kernel') diff --git a/kernel/fork.c b/kernel/fork.c index 2a587b3224e..8a069612eac 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -255,7 +255,6 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) /* * Link in the new vma and copy the page table entries. */ - spin_lock(&mm->page_table_lock); *pprev = tmp; pprev = &tmp->vm_next; @@ -265,7 +264,6 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) mm->map_count++; retval = copy_page_range(mm, oldmm, tmp); - spin_unlock(&mm->page_table_lock); if (tmp->vm_ops && tmp->vm_ops->open) tmp->vm_ops->open(tmp); -- cgit v1.2.3-18-g5258