From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f181.google.com (mail-we0-f181.google.com [74.125.82.181]) by kanga.kvack.org (Postfix) with ESMTP id 62B99829A8 for ; Tue, 6 May 2014 11:30:32 -0400 (EDT) Received: by mail-we0-f181.google.com with SMTP id w61so2194634wes.26 for ; Tue, 06 May 2014 08:30:31 -0700 (PDT) Received: from mail-wg0-f52.google.com (mail-wg0-f52.google.com [74.125.82.52]) by mx.google.com with ESMTPS id a2si4652014wix.9.2014.05.06.08.30.30 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 06 May 2014 08:30:30 -0700 (PDT) Received: by mail-wg0-f52.google.com with SMTP id l18so8102101wgh.23 for ; Tue, 06 May 2014 08:30:30 -0700 (PDT) From: Steve Capper Subject: [RFC PATCH V5 3/6] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Date: Tue, 6 May 2014 16:30:06 +0100 Message-Id: <1399390209-1756-4-git-send-email-steve.capper@linaro.org> In-Reply-To: <1399390209-1756-1-git-send-email-steve.capper@linaro.org> References: <1399390209-1756-1-git-send-email-steve.capper@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, linux@arm.linux.org.uk, linux-arch@vger.kernel.org, linux-mm@kvack.org Cc: will.deacon@arm.com, gary.robertson@linaro.org, christoffer.dall@linaro.org, peterz@infradead.org, anders.roxell@linaro.org, akpm@linux-foundation.org, Steve Capper In order to implement fast_get_user_pages we need to ensure that the page table walker is protected from page table pages being freed from under it. One way to achieve this is to have the walker disable interrupts, and rely on IPIs from the TLB flushing code blocking before the page table pages are freed. On some ARM platforms we have hardware TLB invalidation, thus the TLB flushing code won't necessarily broadcast IPIs. Also spuriously broadcasting IPIs can hurt system performance if done too often. This problem has already been solved on PowerPC and Sparc by batching up page table pages belonging to more than one mm_user, then scheduling an rcu_sched callback to free the pages. If one were to disable interrupts, that would delay the scheduling interrupts thus block the page table pages being freed. This logic has also been promoted to core code and is activated when one enables HAVE_RCU_TABLE_FREE. This patch enables HAVE_RCU_TABLE_FREE and incorporates it into the existing ARM TLB logic. Signed-off-by: Steve Capper --- arch/arm/Kconfig | 1 + arch/arm/include/asm/tlb.h | 38 ++++++++++++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index db3c541..6cfdb3b 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -59,6 +59,7 @@ config ARM select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_RCU_TABLE_FREE if (SMP && CPU_V7) select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_SYSCALL_TRACEPOINTS select HAVE_UID16 diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h index f1a0dac..3cadb72 100644 --- 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 unsigned int fullmm; struct vm_area_struct *vma; unsigned long start, end; @@ -101,6 +128,9 @@ static inline void __tlb_alloc_page(struct mmu_gather *tlb) static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb) { tlb_flush(tlb); +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb_table_flush(tlb); +#endif } static inline void tlb_flush_mmu_free(struct mmu_gather *tlb) @@ -129,6 +159,10 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start tlb->pages = tlb->local; tlb->nr = 0; __tlb_alloc_page(tlb); + +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb->batch = NULL; +#endif } static inline void @@ -205,7 +239,7 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, tlb_add_flush(tlb, addr + SZ_1M); #endif - tlb_remove_page(tlb, pte); + tlb_remove_entry(tlb, pte); } static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, @@ -213,7 +247,7 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, { #ifdef CONFIG_ARM_LPAE tlb_add_flush(tlb, addr); - tlb_remove_page(tlb, virt_to_page(pmdp)); + tlb_remove_entry(tlb, virt_to_page(pmdp)); #endif } -- 1.8.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org