linux-kernel - Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func

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Date:   Wed, 21 Jun 2017 19:27:44 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Nadav Amit <nadav.amit@...il.com>, Ingo Molnar <mingo@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common()

On Wed, Jun 21, 2017 at 4:26 PM, Nadav Amit <nadav.amit@...il.com> wrote:
> Andy Lutomirski <luto@...nel.org> 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?

--Andy