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/i386/mm/ioremap.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'arch/i386/mm') diff --git a/arch/i386/mm/ioremap.c b/arch/i386/mm/ioremap.c index f379b8d67558..5d09de8d1c6b 100644 --- a/arch/i386/mm/ioremap.c +++ b/arch/i386/mm/ioremap.c @@ -28,7 +28,7 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long pfn; pfn = phys_addr >> PAGE_SHIFT; - pte = pte_alloc_kernel(&init_mm, pmd, addr); + pte = pte_alloc_kernel(pmd, addr); if (!pte) return -ENOMEM; do { @@ -87,14 +87,12 @@ static int ioremap_page_range(unsigned long addr, flush_cache_all(); phys_addr -= addr; pgd = pgd_offset_k(addr); - spin_lock(&init_mm.page_table_lock); do { next = pgd_addr_end(addr, end); err = ioremap_pud_range(pgd, addr, next, phys_addr+addr, flags); if (err) break; } while (pgd++, addr = next, addr != end); - spin_unlock(&init_mm.page_table_lock); flush_tlb_all(); return err; } -- cgit v1.2.1