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

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Date:	Tue, 24 Sep 2013 10:15:43 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Mike Travis <travis@....com>,
	Jason Wessel <jason.wessel@...driver.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jason Wessel <jason.wessel@...driver.com>,
	"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.


* Mike Travis <travis@....com> 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>
> ---
>  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, any objections to form or substance of this callback?

Thanks,

	Ingo
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