src/patches/60066_xen-x86-exit-mmap.patch1

   1 Subject: be more aggressive about de-activating mm-s under destruction
   2 From: jbeulich@novell.com
   3 Patch-mainline: obsolete
   4
   5 ... by not only handling the current task on the CPU arch_exit_mmap()
   6 gets executed on, but also forcing remote CPUs to do so.
   7
   8 Index: head-2008-12-01/arch/x86/mm/pgtable-xen.c
   9 ===================================================================
  10 --- head-2008-12-01.orig/arch/x86/mm/pgtable-xen.c      2008-12-01 12:13:06.000000000 +0100
  11 +++ head-2008-12-01/arch/x86/mm/pgtable-xen.c   2008-12-01 12:13:16.000000000 +0100
  12 @@ -418,27 +418,44 @@ void arch_dup_mmap(struct mm_struct *old
  13                 mm_pin(mm);
  14  }
  15
  16 -void arch_exit_mmap(struct mm_struct *mm)
  17 +/*
  18 + * We aggressively remove defunct pgd from cr3. We execute unmap_vmas() *much*
  19 + * faster this way, as no hypercalls are needed for the page table updates.
  20 + */
  21 +static void leave_active_mm(struct task_struct *tsk, struct mm_struct *mm)
  22 +       __releases(tsk->alloc_lock)
  23  {
  24 -       struct task_struct *tsk = current;
  25 -
  26 -       task_lock(tsk);
  27 -
  28 -       /*
  29 -        * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
  30 -        * *much* faster this way, as no tlb flushes means bigger wrpt batches.
  31 -        */
  32         if (tsk->active_mm == mm) {
  33                 tsk->active_mm = &init_mm;
  34                 atomic_inc(&init_mm.mm_count);
  35
  36                 switch_mm(mm, &init_mm, tsk);
  37
  38 -               atomic_dec(&mm->mm_count);
  39 -               BUG_ON(atomic_read(&mm->mm_count) == 0);
  40 +               if (atomic_dec_and_test(&mm->mm_count))
  41 +                       BUG();
  42         }
  43
  44         task_unlock(tsk);
  45 +}
  46 +
  47 +static void _leave_active_mm(void *mm)
  48 +{
  49 +       struct task_struct *tsk = current;
  50 +
  51 +       if (spin_trylock(&tsk->alloc_lock))
  52 +               leave_active_mm(tsk, mm);
  53 +}
  54 +
  55 +void arch_exit_mmap(struct mm_struct *mm)
  56 +{
  57 +       struct task_struct *tsk = current;
  58 +
  59 +       task_lock(tsk);
  60 +       leave_active_mm(tsk, mm);
  61 +
  62 +       preempt_disable();
  63 +       smp_call_function_mask(mm->cpu_vm_mask, _leave_active_mm, mm, 1);
  64 +       preempt_enable();
  65
  66         if (PagePinned(virt_to_page(mm->pgd))
  67             && atomic_read(&mm->mm_count) == 1