Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP
Date	2016-11-08 22:20 +0100
Message-ID	<sBlYd-6oS-1@gated-at.bofh.it> (permalink)
References	(3 earlier) <sAWwO-6Ln-43@gated-at.bofh.it> <sAWZQ-6Y4-25@gated-at.bofh.it> <sBj0m-4ko-35@gated-at.bofh.it> <sBlvb-5XM-19@gated-at.bofh.it> <sBlOx-6l2-21@gated-at.bofh.it>
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On Tue, 8 Nov 2016, Borislav Petkov wrote:
> On Tue, Nov 08, 2016 at 09:39:02PM +0100, Thomas Gleixner wrote:
> > That does not make any sense. Where is m.tsc initialized? I couldn't find
> > any place which does, except this and the conditional clear farther down in
> > that function.
> 
> mce_gather_info->mce_setup does
> 
> m->tsc = rdtsc();
> 
> And we do that *everytime* but then we go and clear the damn thing. I
> know, I know, I wanted to flip that logic too and read the TSC *only*
> when we want a precise timestamp but that would require more changes as
> mce_setup() is used at a bunch of places.

And yes, you should spend the extra cycles. Adding a flags argument to
mce_setup() and propagate it through the various callsites shouldn't be
that hard and would make the stuff obvious instead of obfuscated.

Thanks,

	tglx

Thread

[RFC PATCH 0/3] x86/RAS: Dump error record to dmesg if no consumers Borislav Petkov <bp@alien8.de> - 2016-11-01 13:20 +0100
  [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-05 14:20 +0100
    RE: [PATCH] x86/MCE: Remove MCP_TIMESTAMP "Luck, Tony" <tony.luck@intel.com> - 2016-11-07 18:50 +0100
      Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-07 19:10 +0100
        RE: [PATCH] x86/MCE: Remove MCP_TIMESTAMP "Luck, Tony" <tony.luck@intel.com> - 2016-11-07 19:40 +0100
          Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-08 19:10 +0100
            RE: [PATCH] x86/MCE: Remove MCP_TIMESTAMP "Luck, Tony" <tony.luck@intel.com> - 2016-11-08 19:30 +0100
            Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Thomas Gleixner <tglx@linutronix.de> - 2016-11-08 21:50 +0100
              Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-08 22:10 +0100
                Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Thomas Gleixner <tglx@linutronix.de> - 2016-11-08 22:20 +0100
                Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-08 22:30 +0100
                Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Thomas Gleixner <tglx@linutronix.de> - 2016-11-08 23:00 +0100
                Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP Borislav Petkov <bp@alien8.de> - 2016-11-09 19:10 +0100
  Re: [RFC PATCH 0/3] x86/RAS: Dump error record to dmesg if no  consumers Ingo Molnar <mingo@kernel.org> - 2016-11-07 08:40 +0100

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