On Thu, 13 Dec 2007, Siddha, Suresh B wrote: > <snip> > Oh, and I see what's wrong: you not only switched "free_page()" to > "quicklist_free()", you *also* switched "tlb_remove_page()" to > "quicklist_free()". > </snip> > > The above comment is in reference to below portion of code: > > -#define __pte_free_tlb(tlb,pte) tlb_remove_page((tlb),(pte)) > +#define __pte_free_tlb(tlb,pte) quicklist_free_page(QUICK_PT, NULL,(pte)) > > tlb_remove_page() was marking tlb->need_flush. Which is later used > by tlb_flush_mmu(). With quicklist_free_page() we loose all that..
Aha. So we need to flush if there is a page on the quicklist. Patch follows. > Now in a corner case scenario with a big munmap() which calls unmap_region() > and if it so happens that the region getting unmapped just has page > tables setup but with all PTE's set to NULL, unmap_region() may > potentially free the page table pages > [ tlb_finish_mmu() calls check_pgt_cache() which trims quicklist ] > with out flushing the TLB's. > [ (tlb_finish_mmu() calls the tlb_flush_mmu() but it will not do > much as need_flush is not set ] > > Similarly Linus brought pre-emptions issues associated with quicklist usage.. AFAICT page table shootdown cannot be preempted. What where the preemption issues? Index: linux-2.6/include/asm-generic/tlb.h =================================================================== --- linux-2.6.orig/include/asm-generic/tlb.h 2007-12-13 14:45:38.000000000 -0800 +++ linux-2.6/include/asm-generic/tlb.h 2007-12-13 14:51:07.000000000 -0800 @@ -14,6 +14,7 @@ #define _ASM_GENERIC__TLB_H #include <linux/swap.h> +#include <linux/quicklist.h> #include <asm/pgalloc.h> #include <asm/tlbflush.h> @@ -85,6 +86,9 @@ tlb_flush_mmu(struct mmu_gather *tlb, un static inline void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end) { +#ifdef CONFIG_QUICKLIST + tlb->need_flush += &__get_cpu_var(quicklist)[0].nr_pages != 0; +#endif tlb_flush_mmu(tlb, start, end); /* keep the page table cache within bounds */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/