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arch, mm: Remove tlb_fast_mode()

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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>
This commit is contained in:
Peter Zijlstra 2013-06-05 12:26:50 +02:00 committed by Linus Torvalds
parent 2c95523c0f
commit 29eb77825c
4 changed files with 13 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
arch/arm/include/asm/tlb.h
View File

@ -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;

41
arch/ia64/include/asm/tlb.h
View File

@ -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);

17
include/asm-generic/tlb.h
View File

@ -97,11 +97,9 @@ struct mmu_gather {
unsigned long start;
unsigned long end;
unsigned int need_flush : 1, /* Did free PTEs */
fast_mode : 1; /* No batching */
/* we are in the middle of an operation to clear
* a full mm and can make some optimizations */
unsigned int fullmm : 1,
fullmm : 1,
/* we have performed an operation which
* requires a complete flush of the tlb */
need_flush_all : 1;
@ -114,19 +112,6 @@ struct mmu_gather {
#define HAVE_GENERIC_MMU_GATHER
static inline int tlb_fast_mode(struct mmu_gather *tlb)
{
#ifdef CONFIG_SMP
return tlb->fast_mode;
#else
/*
* For UP we don't need to worry about TLB flush
* and page free order so much..
*/
return 1;
#endif
}
void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
void tlb_flush_mmu(struct mmu_gather *tlb);
void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,

9
mm/memory.c
View File

@ -220,7 +220,6 @@ void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
tlb->start = -1UL;
tlb->end = 0;
tlb->need_flush = 0;
tlb->fast_mode = (num_possible_cpus() == 1);
tlb->local.next = NULL;
tlb->local.nr = 0;
tlb->local.max = ARRAY_SIZE(tlb->__pages);
@ -244,9 +243,6 @@ void tlb_flush_mmu(struct mmu_gather *tlb)
tlb_table_flush(tlb);
#endif
if (tlb_fast_mode(tlb))
return;
for (batch = &tlb->local; batch; batch = batch->next) {
free_pages_and_swap_cache(batch->pages, batch->nr);
batch->nr = 0;
@ -288,11 +284,6 @@ int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
VM_BUG_ON(!tlb->need_flush);
if (tlb_fast_mode(tlb)) {
free_page_and_swap_cache(page);
return 1; /* avoid calling tlb_flush_mmu() */
}
batch = tlb->active;
batch->pages[batch->nr++] = page;
if (batch->nr == batch->max) {