linux-kernel - [RFC][PATCH v2 -next 0/2] make pstore/kmsg_dump run after stopping other cpus in panic path

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Message-ID: <5C4C569E8A4B9B42A84A977CF070A35B2C576122A6@USINDEVS01.corp.hds.com>
Date:	Fri, 21 Oct 2011 17:19:04 -0400
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	"Chen, Gong" <gong.chen@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Matthew Garrett <mjg@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"ying.huang@...el.com" <ying.huang@...el.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"hughd@...omium.org" <hughd@...omium.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"namhyung@...il.com" <namhyung@...il.com>,
	Don Zickus <dzickus@...hat.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH v2 -next 0/2] make pstore/kmsg_dump run after stopping
 other cpus in panic path

Hi,

 As Don mentioned in following thread, it would be nice for pstore/kmsg_dump to serialize 
 panic path and have one cpu running  because they can log messages reliably. 
 
 https://lkml.org/lkml/2011/10/13/427
 
 For realizing this idea, we have to move kmsg_dump below smp_send_stop() and bust some locks of 
 kmsg_dump/pstore in panic path. Also, we have to care about NMI interrupt.

Changelog:
 v2
  - Adding trylocks to kmsg_dump()/pstore_dump() so that they can work in NMI context.  
  - Dividing a patch into two. 
     First one is just moving kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop().
     Second one is changing lock operations in kmsg_dump()/pstore_dump().
 v1
  - moving kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop.
  - busting logbuf_lock of kmsg_dump() in panic path for avoiding deadlock.
  - busting psinfo->buf_lock of pstore_dump() in panic path for avoiding deadlock.

Patch Descriptions:
[RFC][PATCH -next v2 1/2] Moving kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop()
  - moving kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop for serializing logging 
    process via smp_send_stop.

[RFC][PATCH v2 -next 2/2] Adding lock operations to kmsg_dump()/pstore_dump()
  Adding a lock operation below in pstore_dump()
  - busting psinfo->buf_lock of pstore_dump() in panic path for avoiding deadlock.

  Adding lock operations below in kmsg_dump()
  - busting logbuf_lock of kmsg_dump() in panic path for avoiding deadlock.
  - Adding trylock for taking logbuf_lock of kmsg_dump() in NMI context. 

Seiji
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