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authorPeter Zijlstra <peterz@infradead.org>2013-06-05 12:26:50 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2013-06-06 10:07:26 +0900
commit29eb77825cc7da8d45b642de2de3d423dc8a363f (patch)
tree689c3c9f8b34f8023899ba8c230ea04c4dc21e54 /arch
parent2c95523c0f0ca7c2f157a07f0c03b6bbba13fee6 (diff)
arch, mm: Remove tlb_fast_mode()
Since the introduction of preemptible mmu_gather TLB fast mode has been broken. TLB fast mode relies on there being absolutely no concurrency; it frees pages first and invalidates TLBs later. However now we can get concurrency and stuff goes *bang*. This patch removes all tlb_fast_mode() code; it was found the better option vs trying to patch the hole by entangling tlb invalidation with the scheduler. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Russell King <linux@arm.linux.org.uk> Cc: Tony Luck <tony.luck@intel.com> Reported-by: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/include/asm/tlb.h27
-rw-r--r--arch/ia64/include/asm/tlb.h41
2 files changed, 12 insertions, 56 deletions
diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index 99a19512ee2..bdf2b8458ec 100644
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -33,18 +33,6 @@
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
-/*
- * We need to delay page freeing for SMP as other CPUs can access pages
- * which have been removed but not yet had their TLB entries invalidated.
- * Also, as ARMv7 speculative prefetch can drag new entries into the TLB,
- * we need to apply this same delaying tactic to ensure correct operation.
- */
-#if defined(CONFIG_SMP) || defined(CONFIG_CPU_32v7)
-#define tlb_fast_mode(tlb) 0
-#else
-#define tlb_fast_mode(tlb) 1
-#endif
-
#define MMU_GATHER_BUNDLE 8
/*
@@ -112,12 +100,10 @@ static inline void __tlb_alloc_page(struct mmu_gather *tlb)
static inline void tlb_flush_mmu(struct mmu_gather *tlb)
{
tlb_flush(tlb);
- if (!tlb_fast_mode(tlb)) {
- free_pages_and_swap_cache(tlb->pages, tlb->nr);
- tlb->nr = 0;
- if (tlb->pages == tlb->local)
- __tlb_alloc_page(tlb);
- }
+ free_pages_and_swap_cache(tlb->pages, tlb->nr);
+ tlb->nr = 0;
+ if (tlb->pages == tlb->local)
+ __tlb_alloc_page(tlb);
}
static inline void
@@ -178,11 +164,6 @@ tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
{
- if (tlb_fast_mode(tlb)) {
- free_page_and_swap_cache(page);
- return 1; /* avoid calling tlb_flush_mmu */
- }
-
tlb->pages[tlb->nr++] = page;
VM_BUG_ON(tlb->nr > tlb->max);
return tlb->max - tlb->nr;
diff --git a/arch/ia64/include/asm/tlb.h b/arch/ia64/include/asm/tlb.h
index c3ffe3e54ed..ef3a9de0195 100644
--- a/arch/ia64/include/asm/tlb.h
+++ b/arch/ia64/include/asm/tlb.h
@@ -46,12 +46,6 @@
#include <asm/tlbflush.h>
#include <asm/machvec.h>
-#ifdef CONFIG_SMP
-# define tlb_fast_mode(tlb) ((tlb)->nr == ~0U)
-#else
-# define tlb_fast_mode(tlb) (1)
-#endif
-
/*
* If we can't allocate a page to make a big batch of page pointers
* to work on, then just handle a few from the on-stack structure.
@@ -60,7 +54,7 @@
struct mmu_gather {
struct mm_struct *mm;
- unsigned int nr; /* == ~0U => fast mode */
+ unsigned int nr;
unsigned int max;
unsigned char fullmm; /* non-zero means full mm flush */
unsigned char need_flush; /* really unmapped some PTEs? */
@@ -103,6 +97,7 @@ extern struct ia64_tr_entry *ia64_idtrs[NR_CPUS];
static inline void
ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
+ unsigned long i;
unsigned int nr;
if (!tlb->need_flush)
@@ -141,13 +136,11 @@ ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long e
/* lastly, release the freed pages */
nr = tlb->nr;
- if (!tlb_fast_mode(tlb)) {
- unsigned long i;
- tlb->nr = 0;
- tlb->start_addr = ~0UL;
- for (i = 0; i < nr; ++i)
- free_page_and_swap_cache(tlb->pages[i]);
- }
+
+ tlb->nr = 0;
+ tlb->start_addr = ~0UL;
+ for (i = 0; i < nr; ++i)
+ free_page_and_swap_cache(tlb->pages[i]);
}
static inline void __tlb_alloc_page(struct mmu_gather *tlb)
@@ -167,20 +160,7 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned int full_m
tlb->mm = mm;
tlb->max = ARRAY_SIZE(tlb->local);
tlb->pages = tlb->local;
- /*
- * Use fast mode if only 1 CPU is online.
- *
- * It would be tempting to turn on fast-mode for full_mm_flush as well. But this
- * doesn't work because of speculative accesses and software prefetching: the page
- * table of "mm" may (and usually is) the currently active page table and even
- * though the kernel won't do any user-space accesses during the TLB shoot down, a
- * compiler might use speculation or lfetch.fault on what happens to be a valid
- * user-space address. This in turn could trigger a TLB miss fault (or a VHPT
- * walk) and re-insert a TLB entry we just removed. Slow mode avoids such
- * problems. (We could make fast-mode work by switching the current task to a
- * different "mm" during the shootdown.) --davidm 08/02/2002
- */
- tlb->nr = (num_online_cpus() == 1) ? ~0U : 0;
+ tlb->nr = 0;
tlb->fullmm = full_mm_flush;
tlb->start_addr = ~0UL;
}
@@ -214,11 +194,6 @@ static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
{
tlb->need_flush = 1;
- if (tlb_fast_mode(tlb)) {
- free_page_and_swap_cache(page);
- return 1; /* avoid calling tlb_flush_mmu */
- }
-
if (!tlb->nr && tlb->pages == tlb->local)
__tlb_alloc_page(tlb);