[RFC V2 PATCH 0/1] kexec: crash_kexec_post_notifiers boot option related fixes

[Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>]

This is a bugfix patch for crash_kexec_post_notifiers boot option
which allows users to call panic notifiers and kmsg dumpers before
kdump.

This fixes one of the problems reported by Daniel Walker
(https://lkml.org/lkml/2015/6/24/44). 

 Problem 1:
 If crash_kexec_post_notifiers boot option is specified, some
 shutting down process which assume other cpus are still alive
 don't work properly.

 Problem 2 (addressed by this patch):
 If crash_kexec_post_notifiers boot option is specified, register
 information of other cpus are not saved to crash dumps.

Following Vivek's opinion, this patch replaces smp_send_stop()
in panic() with suitable version for crash_kexec which saves
cpu states and other things like cleaning up VMX/SVM.  Since this
needs architecture specific implementation and it's not so trivial,
this version only support for x86.  So the problem 1, known to
happen on MIPS/OCTEON, is not addressed now.

To keep the modification impact low, this patch doesn't change
the logic basically if crash_kexec_post_notifiers is not specified.

Please note that crash_kexec() can be called directly without
entering panic().  Stopping other cpus functionality is still
needed in crash_kexec().

Changes in V2:
- Replace smp_send_stop() call with crash_kexec version which
  saves cpu states and does cleanups instead of changing execution
  flow
- Drop a fix for Problem 1
- Drop other patches because they aren't needed anymore

V1: https://lkml.org/lkml/2015/7/10/316

---

Hidehiro Kawai (1):
      panic/x86: Replace smp_send_stop() with crash_kexec version


 arch/x86/kernel/crash.c |   16 +++++++++++-----
 kernel/panic.c          |   29 +++++++++++++++++++++++------
 2 files changed, 34 insertions(+), 11 deletions(-)


-- 
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group