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authorAndy Lutomirski <luto@kernel.org>2016-01-06 20:21:01 (GMT)
committerIngo Molnar <mingo@kernel.org>2016-01-11 11:03:15 (GMT)
commit71b3c126e61177eb693423f2e18a1914205b165e (patch)
treea91955974bf8281db543a6ae1fee03ffdc6a9011 /arch/x86/mm
parentafd2ff9b7e1b367172f18ba7f693dfb62bdcb2dc (diff)
downloadlinux-71b3c126e61177eb693423f2e18a1914205b165e.tar.xz
x86/mm: Add barriers and document switch_mm()-vs-flush synchronization
When switch_mm() activates a new PGD, it also sets a bit that tells other CPUs that the PGD is in use so that TLB flush IPIs will be sent. In order for that to work correctly, the bit needs to be visible prior to loading the PGD and therefore starting to fill the local TLB. Document all the barriers that make this work correctly and add a couple that were missing. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/tlb.c29
1 files changed, 26 insertions, 3 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 8ddb5d0..8f4cc3d 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -161,7 +161,10 @@ void flush_tlb_current_task(void)
preempt_disable();
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
+
+ /* This is an implicit full barrier that synchronizes with switch_mm. */
local_flush_tlb();
+
trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
@@ -188,17 +191,29 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
unsigned long base_pages_to_flush = TLB_FLUSH_ALL;
preempt_disable();
- if (current->active_mm != mm)
+ if (current->active_mm != mm) {
+ /* Synchronize with switch_mm. */
+ smp_mb();
+
goto out;
+ }
if (!current->mm) {
leave_mm(smp_processor_id());
+
+ /* Synchronize with switch_mm. */
+ smp_mb();
+
goto out;
}
if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB))
base_pages_to_flush = (end - start) >> PAGE_SHIFT;
+ /*
+ * Both branches below are implicit full barriers (MOV to CR or
+ * INVLPG) that synchronize with switch_mm.
+ */
if (base_pages_to_flush > tlb_single_page_flush_ceiling) {
base_pages_to_flush = TLB_FLUSH_ALL;
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
@@ -228,10 +243,18 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
preempt_disable();
if (current->active_mm == mm) {
- if (current->mm)
+ if (current->mm) {
+ /*
+ * Implicit full barrier (INVLPG) that synchronizes
+ * with switch_mm.
+ */
__flush_tlb_one(start);
- else
+ } else {
leave_mm(smp_processor_id());
+
+ /* Synchronize with switch_mm. */
+ smp_mb();
+ }
}
if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)