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authorHugh Dickins <hugh@veritas.com>2005-10-29 21:16:21 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-30 00:40:40 -0400
commit872fec16d9a0ed3b75b8893aa217e49cca575ee5 (patch)
tree1dfc8b9f2754bdfff645188e497865c00201d535 /arch/ppc/kernel/dma-mapping.c
parent46dea3d092d23a58b42499cc8a21de0fad079f4a (diff)
[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 <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/ppc/kernel/dma-mapping.c')
-rw-r--r--arch/ppc/kernel/dma-mapping.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/arch/ppc/kernel/dma-mapping.c b/arch/ppc/kernel/dma-mapping.c
index 0f710d2baec6..685fd0defe23 100644
--- a/arch/ppc/kernel/dma-mapping.c
+++ b/arch/ppc/kernel/dma-mapping.c
@@ -335,8 +335,6 @@ static int __init dma_alloc_init(void)
335 pte_t *pte; 335 pte_t *pte;
336 int ret = 0; 336 int ret = 0;
337 337
338 spin_lock(&init_mm.page_table_lock);
339
340 do { 338 do {
341 pgd = pgd_offset(&init_mm, CONSISTENT_BASE); 339 pgd = pgd_offset(&init_mm, CONSISTENT_BASE);
342 pmd = pmd_alloc(&init_mm, pgd, CONSISTENT_BASE); 340 pmd = pmd_alloc(&init_mm, pgd, CONSISTENT_BASE);
@@ -347,7 +345,7 @@ static int __init dma_alloc_init(void)
347 } 345 }
348 WARN_ON(!pmd_none(*pmd)); 346 WARN_ON(!pmd_none(*pmd));
349 347
350 pte = pte_alloc_kernel(&init_mm, pmd, CONSISTENT_BASE); 348 pte = pte_alloc_kernel(pmd, CONSISTENT_BASE);
351 if (!pte) { 349 if (!pte) {
352 printk(KERN_ERR "%s: no pte tables\n", __func__); 350 printk(KERN_ERR "%s: no pte tables\n", __func__);
353 ret = -ENOMEM; 351 ret = -ENOMEM;
@@ -357,8 +355,6 @@ static int __init dma_alloc_init(void)
357 consistent_pte = pte; 355 consistent_pte = pte;
358 } while (0); 356 } while (0);
359 357
360 spin_unlock(&init_mm.page_table_lock);
361
362 return ret; 358 return ret;
363} 359}
364 360