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/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index 99a1951..bdf2b84 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_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 @@
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;