On Wed, Aug 27, 2014 at 12:50:10PM +0100, Catalin Marinas wrote:

On Thu, Aug 21, 2014 at 04:43:29PM +0100, Steve Capper wrote:

quoted

--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h

@@ -35,12 +35,39 @@
 
 #define MMU_GATHER_BUNDLE	8
 
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+static inline void __tlb_remove_table(void *_table)
+{
+	free_page_and_swap_cache((struct page *)_table);
+}
+
+struct mmu_table_batch {
+	struct rcu_head		rcu;
+	unsigned int		nr;
+	void			*tables[0];
+};
+
+#define MAX_TABLE_BATCH		\
+	((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
+
+extern void tlb_table_flush(struct mmu_gather *tlb);
+extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
+
+#define tlb_remove_entry(tlb, entry)	tlb_remove_table(tlb, entry)
+#else
+#define tlb_remove_entry(tlb, entry)	tlb_remove_page(tlb, entry)
+#endif /* CONFIG_HAVE_RCU_TABLE_FREE */
+
 /*
  * TLB handling.  This allows us to remove pages from the page
  * tables, and efficiently handle the TLB issues.
  */
 struct mmu_gather {
 	struct mm_struct	*mm;
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+	struct mmu_table_batch	*batch;
+	unsigned int		need_flush;
+#endif

We add need_flush here just because it is set by tlb_remove_table() but
it won't actually be checked by anything since arch/arm uses its own
version of tlb_flush_mmu(). But I wouldn't go for #ifdefs in the core
code either.

We should (as a separate patchset) convert arch/arm to generic
mmu_gather. I know Russell had objections in the past but mmu_gather has
evolved since and it's not longer inefficient (I think the only case is
shift_arg_pages but that's pretty much lost in the noise).

I would be happy to help out with a conversion to generic mmu_gather if
it's wanted for arm.

For this patch:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Cheers.

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