Date: Fri, 21 Nov 2014 14:23:01 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>, Tejun Heo <tj@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Don Zickus <dzickus@redhat.com>, Dave Jones <davej@redhat.com>,
        "the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: frequent lockups in 3.18rc4
Message-ID: <20141121142301.564f7eb7@gandalf.local.home>
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On Fri, 21 Nov 2014 11:06:41 -0800
Linus Torvalds <torvalds@linux-foundation.org> wrote:
 
>   static noinline int vmalloc_fault(unsigned long address)
>   {
>         pgd_t *pgd_dst;
>         pgdval_t pgd_entry;
>         unsigned index = pgd_index(address);
> 
>         if (index < KERNEL_PGD_BOUNDARY)
>                 return -1;
> 
>         pgd_entry = init_mm.pgd[index].pgd;
>         if (!pgd_entry)
>                 return -1;

Should we at least check to see if it is present?

	if (!(pgd_entry & 1))
		return -1;

?

-- Steve

> 
>         pgd_dst = __va(PAGE_MASK & read_cr3());
>         pgd_dst += index;
> 
>         if (pgd_dst->pgd)
>                 return -1;
> 
>         ACCESS_ONCE(pgd_dst->pgd) = pgd_entry;
>         return 0;
>   }
>   NOKPROBE_SYMBOL(vmalloc_fault);
> 
> Hmm? Does anybody see anything fundamentally wrong with this?
> 
>                      Linus

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