* Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> On Wed, Jun 21, 2017 at 4:26 PM, Nadav Amit <nadav.amit@xxxxxxxxx> wrote:
> > Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> >
> >> index 2a5e851f2035..f06239c6919f 100644
> >> --- a/arch/x86/mm/tlb.c
> >> +++ b/arch/x86/mm/tlb.c
> >> @@ -208,6 +208,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
> >> static void flush_tlb_func_common(const struct flush_tlb_info *f,
> >> bool local, enum tlb_flush_reason reason)
> >> {
> >> + /* This code cannot presently handle being reentered. */
> >> + VM_WARN_ON(!irqs_disabled());
> >> +
> >> if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) {
> >> leave_mm(smp_processor_id());
> >> return;
> >> @@ -313,8 +316,12 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
> >> info.end = TLB_FLUSH_ALL;
> >> }
> >>
> >> - if (mm == this_cpu_read(cpu_tlbstate.loaded_mm))
> >> + if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
> >
> > Perhaps you want to add:
> >
> > VM_WARN_ON(irqs_disabled());
> >
> > here
> >
> >> + local_irq_disable();
> >> flush_tlb_func_local(&info, TLB_LOCAL_MM_SHOOTDOWN);
> >> + local_irq_enable();
> >> + }
> >> +
> >> if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
> >> flush_tlb_others(mm_cpumask(mm), &info);
> >> put_cpu();
> >> @@ -370,8 +377,12 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
> >>
> >> int cpu = get_cpu();
> >>
> >> - if (cpumask_test_cpu(cpu, &batch->cpumask))
> >> + if (cpumask_test_cpu(cpu, &batch->cpumask)) {
> >
> > and here?
> >
>
> Will do.
>
> What I really want is lockdep_assert_irqs_disabled() or, even better,
> for this to be implicit when calling local_irq_disable(). Ingo?
I tried that once many years ago and IIRC there were problems - but maybe we could
try it again and enforce it, as I agree that the following pattern:
local_irq_disable();
...
local_irq_disable();
...
local_irq_enable();
...
local_irq_enable();
.. is actively dangerous.
Thanks,
Ingo
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