Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8

From	Jeff Merkey <linux.mdb@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8
Date	2016-01-30 20:00 +0100
Message-ID	<qWIUy-84T-5@gated-at.bofh.it> (permalink)
References	(4 earlier) <qWz4S-8oS-9@gated-at.bofh.it> <qWzoe-5x-1@gated-at.bofh.it> <qWH2r-6AY-19@gated-at.bofh.it> <qWHYu-7qu-9@gated-at.bofh.it> <qWHYv-7qu-21@gated-at.bofh.it>
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>
> Just so you know, I have no intention of supporting this use case.  In
> fact, I'm planning to eventually stop using IST for #DB entirely, at
> which point the kernel will crash terribly if this code is
> single-stepped (except when using a hypervisor to do this single
> stepping, which is a much more sensible way to handle it).

I don't know what good using the userspace trap code is going to
help with this, a hypervisor will crash too with sysret being used
there -- I just tested it.

So it breaks all debuggers, even the faux ones that run as user space
apps.  Your
other suggestions will cause some mayhem too for debuggers.  If you
break something, I'll just unpatch it in my tree, so have fun.  LOL

Jeff

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Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 09:30 +0100
  Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 09:50 +0100
    Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Andy Lutomirski <luto@amacapital.net> - 2016-01-30 18:00 +0100
      Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 19:00 +0100
        Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Andy Lutomirski <luto@amacapital.net> - 2016-01-30 19:00 +0100
          Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 19:10 +0100
            Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 19:20 +0100
          Re: [BUG REPORT] Soft Lockup in smp_call_function_single+0xD8 Jeff Merkey <linux.mdb@gmail.com> - 2016-01-30 20:00 +0100

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