Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking
Date	2016-04-30 00:50 +0200
Message-ID	<rtpot-5CD-1@gated-at.bofh.it> (permalink)
References	(4 earlier) <rtn3k-3Ce-11@gated-at.bofh.it> <rtnd0-3HL-37@gated-at.bofh.it> <rtnmG-3LT-21@gated-at.bofh.it> <rto93-4rM-5@gated-at.bofh.it> <rtoiK-4yd-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, Apr 29, 2016 at 02:37:41PM -0700, Andy Lutomirski wrote:
> On Fri, Apr 29, 2016 at 2:25 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > I think the easiest way to make it work would be to modify the idtentry
> > macro to put all the idt entries in a dedicated section.  Then the
> > unwinder could easily detect any calls from that code.
> 
> That would work.  Would it make sense to do the same for the irq entries?

Yes, I think so.

> >> I suppose we could try to rejigger the code so that rbp points to
> >> pt_regs or similar.
> >
> > I think we should avoid doing something like that because it would break
> > gdb and all the other unwinders who don't know about it.
> 
> How so?
> 
> Currently, rbp in the entry code is meaningless.  I'm suggesting that,
> when we do, for example, 'call \do_sym' in idtentry, we point rbp to
> the pt_regs.  Currently it points to something stale (which the
> dump_stack code might be relying on.  Hmm.)  But it's probably also
> safe to assume that if you unwind to the 'call \do_sym', then pt_regs
> is the next thing on the stack, so just doing the section thing would
> work.

Yes, rbp is meaningless on the entry from user space.  But if an
in-kernel interrupt occurs (e.g. page fault, preemption) and you have
nested entry, rbp keeps its old value, right?  So the unwinder can walk
past the nested entry frame and keep going until it gets to the original
entry.

> We should really re-add DWARF some day.

Working on it :-)

-- 
Josh

Thread

[RFC PATCH v2 00/18] livepatch: hybrid consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
  [RFC PATCH v2 14/18] livepatch: remove unnecessary object loaded check Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
  [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING thread flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
    Re: [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING  thread flag Petr Mladek <pmladek@suse.com> - 2016-05-03 11:10 +0200
      Re: [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING  thread flag Miroslav Benes <mbenes@suse.cz> - 2016-05-03 14:10 +0200
  [RFC PATCH v2 16/18] livepatch: store function sizes Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
  [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
    Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 20:10 +0200
      Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:20 +0200
        Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:30 +0200
          Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:40 +0200
            Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 23:30 +0200
              Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 23:40 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Jiri Kosina <jikos@kernel.org> - 2016-04-30 00:20 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 01:00 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:20 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 00:50 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:10 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 16:00 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-02 18:00 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 19:40 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-02 20:20 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Ingo Molnar <mingo@kernel.org> - 2016-05-02 20:40 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 21:50 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Jiri Kosina <jikos@kernel.org> - 2016-05-02 22:00 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Jiri Kosina <jikos@kernel.org> - 2016-05-02 22:10 +0200
                Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-03 02:50 +0200
                RE: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking David Laight <David.Laight@ACULAB.COM> - 2016-05-04 17:20 +0200
      Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ  tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:20 +0200
  [RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
    Re: [RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread flag Andy Lutomirski <luto@amacapital.net> - 2016-04-29 20:10 +0200
      Re: [RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread  flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:20 +0200
  [RFC PATCH v2 02/18] x86/asm/head: use a common function for starting CPUs Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
  [RFC PATCH v2 13/18] livepatch: separate enabled and patched states Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
    Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched  states Petr Mladek <pmladek@suse.com> - 2016-05-03 11:40 +0200
      Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched  states Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-03 15:50 +0200
  [RFC PATCH v2 06/18] x86: dump_trace() error handling Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
    Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling Minfei Huang <mnghuan@gmail.com> - 2016-04-29 15:50 +0200
      Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 16:10 +0200
  [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
    Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Brian Gerst <brgerst@gmail.com> - 2016-04-29 20:50 +0200
      Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:30 +0200
    Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Andy Lutomirski <luto@kernel.org> - 2016-04-29 21:40 +0200
      Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 23:00 +0200
        Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Andy Lutomirski <luto@amacapital.net> - 2016-04-29 23:40 +0200
          Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 01:30 +0200
            Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the  stack for idle tasks Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:20 +0200
  [RFC PATCH v2 04/18] x86: move _stext marker before head code Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
  [RFC PATCH v2 01/18] x86/asm/head: clean up initial stack variable Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
  Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Petr Mladek <pmladek@suse.com> - 2016-05-04 10:50 +0200
    Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 18:00 +0200
      Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Miroslav Benes <mbenes@suse.cz> - 2016-05-05 11:50 +0200
      Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Petr Mladek <pmladek@suse.com> - 2016-05-05 15:10 +0200
  barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task  consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 14:40 +0200
    Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Peter Zijlstra <peterz@infradead.org> - 2016-05-04 16:00 +0200
      Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:00 +0200
    Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 16:20 +0200
      Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:30 +0200
        Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 13:30 +0200
        Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Miroslav Benes <mbenes@suse.cz> - 2016-05-09 17:50 +0200
    Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:10 +0200
      Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 12:30 +0200
  klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 16:50 +0200
    Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to  a per-task consistency model Jiri Kosina <jikos@kernel.org> - 2016-05-04 17:00 +0200
    Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 20:00 +0200
      Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 14:00 +0200
        Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-06 14:40 +0200
          Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a  per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-09 14:30 +0200
  Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Petr Mladek <pmladek@suse.com> - 2016-05-06 13:40 +0200
    Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-06 14:50 +0200
  Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Miroslav Benes <mbenes@suse.cz> - 2016-05-09 11:50 +0200
  Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency  model Miroslav Benes <mbenes@suse.cz> - 2016-05-10 13:50 +0200

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