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Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf

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From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf
Date Sat, 09 Sep 2017 20:50:01 +0200
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On Sat, Sep 9, 2017 at 11:29 AM, Borislav Petkov <bp@alien8.de> wrote:
> On Sat, Sep 09, 2017 at 11:26:27AM -0700, Linus Torvalds wrote:
>> But the fact that that fixes it for you does indicate that it's not
>> just a stale TLB entry or something, it really is some CPU using page
>> tables after they have been free'd and been re-allocated to something
>> else (and *then* they may point to garbage).
>
> Cool, I was trying to think of a good use case how we'd hit that. I
> guess you just gave one. :)

The thing is, even with the delayed TLB flushing, I don't think it
should be *so* delayed that we should be seeing a TLB fill from
garbage page tables.

But the part in Andy's patch that worries me the most is that

+               cpumask_clear_cpu(cpu, mm_cpumask(mm));

in enter_lazy_tlb(). It means that we won't be notified by peopel
invalidating the page tables, and while we then do re-validate the TLB
when we switch back from lazy mode, I still worry. I'm not entirely
convinced by that tlb_gen logic.

I can't actually see anything *wrong* in the tlb_gen logic, but it worries me.

            Linus

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Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-05 09:40 +0200
  Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Peter Zijlstra <peterz@infradead.org> - 2017-09-05 11:00 +0200
    Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-05 12:00 +0200
      Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-06 15:00 +0200
        Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-06 15:20 +0200
          Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-07 08:30 +0200
            Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-08 08:30 +0200
              Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 10:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 11:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 11:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Ingo Molnar <mingo@kernel.org> - 2017-09-08 12:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 12:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 13:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-08 18:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 19:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-08 23:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 00:00 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 01:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 01:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 02:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 03:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@amacapital.net> - 2017-09-09 03:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 20:00 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 08:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 12:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 13:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 15:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 15:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 15:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 16:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 16:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 16:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 16:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 18:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 19:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 19:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 19:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 20:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 20:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 20:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 20:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 21:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-10 06:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@amacapital.net> - 2017-09-10 22:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Peter Zijlstra <peterz@infradead.org> - 2017-09-10 22:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Ingo Molnar <mingo@kernel.org> - 2017-09-17 19:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building  e.g. perf Rik van Riel <riel@redhat.com> - 2017-09-11 03:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-11 03:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building  e.g. perf Rik van Riel <riel@redhat.com> - 2017-09-11 17:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 21:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-12 09:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 10:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 17:00 +0200

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