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

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Date:   Wed, 21 Jun 2017 16:26:43 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     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()

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?

> +		local_irq_disable();
> 		flush_tlb_func_local(&info, TLB_LOCAL_SHOOTDOWN);
> +		local_irq_enable();
> +	}
> +
> 	if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
> 		flush_tlb_others(&batch->cpumask, &info);
> 	cpumask_clear(&batch->cpumask);
> -- 
> 2.9.4