linux-kernel - Re: [PATCH 5/7] KGDB/KDB: add support for external NMI handler to call KGDB/KDB.

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Date:	Thu, 3 Oct 2013 07:45:48 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	Mike Travis <travis@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dimitri Sivanich <sivanich@....com>,
	Hedi Berriche <hedi@....com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] KGDB/KDB: add support for external NMI handler to
 call KGDB/KDB.


* Jason Wessel <jason.wessel@...driver.com> wrote:

> On 09/23/2013 04:25 PM, Mike Travis wrote:
> > This patch adds a kgdb_nmicallin() interface that can be used by
> > external NMI handlers to call the KGDB/KDB handler.  The primary need
> > for this is for those types of NMI interrupts where all the CPUs
> > have already received the NMI signal.  Therefore no send_IPI(NMI)
> > is required, and in fact it will cause a 2nd unhandled NMI to occur.
> > This generates the "Dazed and Confuzed" messages.
> > 
> > Since all the CPUs are getting the NMI at roughly the same time, it's not
> > guaranteed that the first CPU that hits the NMI handler will manage to
> > enter KGDB and set the dbg_master_lock before the slaves start entering.
> > The new argument "send_ready" was added for KGDB to signal the NMI handler
> > to release the slave CPUs for entry into KGDB.
> > 
> > Signed-off-by: Mike Travis <travis@....com>
> > Reviewed-by: Dimitri Sivanich <sivanich@....com>
> > Reviewed-by: Hedi Berriche <hedi@....com>
> 
> One problem that I pointed out before and then you can add 
> 
> Acked-by: Jason Wessel <jason.wessel@...driver.com>
>
> > ---
> >  include/linux/kdb.h             |    1 +
> >  include/linux/kgdb.h            |    1 +
> >  kernel/debug/debug_core.c       |   30 +++++++++++++++++++++++++++++-
> >  kernel/debug/debug_core.h       |    1 +
> >  kernel/debug/kdb/kdb_debugger.c |    5 ++++-
> >  kernel/debug/kdb/kdb_main.c     |    3 +++
> >  6 files changed, 39 insertions(+), 2 deletions(-)

Jason, would you be fine with me merging this via tip:x86/uv with your 
Acked-by? That is the tree where the actual usecase of this callback would 
be merged upstream (v3.13-ish), and most of the other commits are x86/uv 
specific.

Thanks,

	Ingo
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