Messages in this thread Patch in this message | | | Date | Fri, 21 Jan 2005 17:16:48 +0800 | From | zhan rongkai <> | Subject | [PATCH] the page count of buddy seems to be buggy under no MMU |
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This set_page_refs() function is copied from linux-2.6.10 mm/page_alloc.c
static inline void set_page_refs(struct page *page, int order) { #ifdef CONFIG_MMU set_page_count(page, 1); #else int i;
/* * We need to reference all the pages for this order, otherwise if * anyone accesses one of the pages with (get/put) it will be freed. */ for (i = 0; i < (1 << order); i++) set_page_count(page+i, 1); #endif /* CONFIG_MMU */ }
So when we are under no MMU, the __free_pages() function also should de-reference all the pages for this order (order > 0), too. However, the current __free_pages() only decrements the first page's refcount, which will cause __free_pages_ok() to dump stack!
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--- linux-2.6.10.orig/mm/page_alloc.c 2004-12-25 05:33:51.000000000 +0800 +++ linux-2.6.10/mm/page_alloc.c 2005-01-21 17:14:08.000000000 +0800 @@ -786,6 +786,8 @@ free_hot_cold_page(pvec->pages[i], pvec->cold); } +#ifdef CONFIG_MMU + fastcall void __free_pages(struct page *page, unsigned int order) { if (!PageReserved(page) && put_page_testzero(page)) { @@ -796,6 +798,35 @@ } } +#else + +fastcall void __free_pages(struct page *page, unsigned int order) +{ + if (PageReserved(page)) + return; + + if (order == 0) { + if (put_page_testzero(page)) + free_hot_page(page); + } else { + int i, result = 0; + + /* + * We need to de-reference all the pages for this order -- see set_page_refs() + */ + for (i = 0; i < (1 << order); i++) + result += put_page_testzero(page + i); + + if (result) { + if (result != (1 << order)) + BUG(); + __free_pages_ok(page, order); + } + } +} + +#endif /* CONFIG_MMU */ + EXPORT_SYMBOL(__free_pages); fastcall void free_pages(unsigned long addr, unsigned int order) -- Rongkai Zhan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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