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

From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf
Date 2017-09-09 01:30 +0200
Message-ID <unASK-5pn-5@gated-at.bofh.it> (permalink)
References (7 earlier) <unuaD-VM-41@gated-at.bofh.it> <unv6G-1yj-21@gated-at.bofh.it> <unzjZ-4iI-35@gated-at.bofh.it> <unztF-4m3-29@gated-at.bofh.it> <unAzo-5dI-9@gated-at.bofh.it>
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On Fri, Sep 8, 2017 at 4:07 PM, Andy Lutomirski <luto@kernel.org> wrote:
>
> I *think* this is impossible because CPU A's mm_cpumask manipulations
> are atomic and should therefore force out the streaming write buffers,
> but maybe there's some other scenario where this matters.

I don't think atomic memops do that.

They enforce globally visible ordering, but since they happen in the
cache and is not actually visible to outside, that doesn't actually
affect any streaming write buffers.

Then, if somebody else requests a cacheline that we have exclusive
ownership to, the write buffers just need to flush before we give up
that cacheline.

So a locked memory op is *not* serializing, it only enforces memory
ordering. Big difference.

Only fully serializing instructions will serialize with the write
buffers, and they are expensive as hell (partly exactly _due_ to these
kinds of issues).

So this change to delay invalidation does sound fairly scary..

              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 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> - 2017-09-09 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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