From 872fec16d9a0ed3b75b8893aa217e49cca575ee5 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 29 Oct 2005 18:16:21 -0700 Subject: [PATCH] mm: init_mm without ptlock First step in pushing down the page_table_lock. init_mm.page_table_lock has been used throughout the architectures (usually for ioremap): not to serialize kernel address space allocation (that's usually vmlist_lock), but because pud_alloc,pmd_alloc,pte_alloc_kernel expect caller holds it. Reverse that: don't lock or unlock init_mm.page_table_lock in any of the architectures; instead rely on pud_alloc,pmd_alloc,pte_alloc_kernel to take and drop it when allocating a new one, to check lest a racing task already did. Similarly no page_table_lock in vmalloc's map_vm_area. Some temporary ugliness in __pud_alloc and __pmd_alloc: since they also handle user mms, which are converted only by a later patch, for now they have to lock differently according to whether or not it's init_mm. If sources get muddled, there's a danger that an arch source taking init_mm.page_table_lock will be mixed with common source also taking it (or neither take it). So break the rules and make another change, which should break the build for such a mismatch: remove the redundant mm arg from pte_alloc_kernel (ppc64 scrapped its distinct ioremap_mm in 2.6.13). Exceptions: arm26 used pte_alloc_kernel on user mm, now pte_alloc_map; ia64 used pte_alloc_map on init_mm, now pte_alloc_kernel; parisc had bad args to pmd_alloc and pte_alloc_kernel in unused USE_HPPA_IOREMAP code; ppc64 map_io_page forgot to unlock on failure; ppc mmu_mapin_ram and ppc64 im_free took page_table_lock for no good reason. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/frv/mm/dma-alloc.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'arch/frv') diff --git a/arch/frv/mm/dma-alloc.c b/arch/frv/mm/dma-alloc.c index cfc4f97490c6..342823aad758 100644 --- a/arch/frv/mm/dma-alloc.c +++ b/arch/frv/mm/dma-alloc.c @@ -55,21 +55,18 @@ static int map_page(unsigned long va, unsigned long pa, pgprot_t prot) pte_t *pte; int err = -ENOMEM; - spin_lock(&init_mm.page_table_lock); - /* Use upper 10 bits of VA to index the first level map */ pge = pgd_offset_k(va); pue = pud_offset(pge, va); pme = pmd_offset(pue, va); /* Use middle 10 bits of VA to index the second-level map */ - pte = pte_alloc_kernel(&init_mm, pme, va); + pte = pte_alloc_kernel(pme, va); if (pte != 0) { err = 0; set_pte(pte, mk_pte_phys(pa & PAGE_MASK, prot)); } - spin_unlock(&init_mm.page_table_lock); return err; } -- cgit v1.2.3-55-g7522