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>
diff --git a/arch/ia64/include/asm/tlb.h b/arch/ia64/include/asm/tlb.h
index c3ffe3e..ef3a9de 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 @@
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 @@
/* 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->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 @@
{
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);