While backporting 71b3c126e611 ("x86/mm: Add barriers and document switch_mm()-vs-flush synchronization") we stumbled across a possibly missing barrier at flush_tlb_page().
Following the reasoning presented while introducing the synchronization barrier at flush_tlb_mm_range(), for the current->active_mm != mm checkpoint: if (current->active_mm != mm) { /* Synchronize with switch_mm. */ smp_mb(); goto out; } it suggests the same barrier should be introduced for the similar outcome at flush_tlb_page(). This patch add that mentioned missing barrier and documents its case. Suggested-by: Andrea Arcangeli <aarca...@redhat.com> Signed-off-by: Rafael Aquini <aqu...@redhat.com> --- arch/x86/mm/tlb.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 4dbe656..3b4addc 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -375,6 +375,12 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long start) /* Synchronize with switch_mm. */ smp_mb(); } + } else { + /* + * current->active_mm != mm + * Synchronize with switch_mm. + */ + smp_mb(); } if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids) -- 2.5.5