linux-kernel - [PATCH v4 0/2] kexec, panic: Making crash

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Date:   Thu, 30 Jun 2022 23:32:56 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     kexec@...ts.infradead.org, linux-rt-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Eric Biederman <ebiederm@...ssion.com>,
        Arnd Bergmann <arnd@...db.de>, Petr Mladek <pmladek@...e.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Juri Lelli <jlelli@...hat.com>,
        "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Subject: [PATCH v4 0/2] kexec, panic: Making crash_kexec() NMI safe

Hi folks,

Here's ~v3~ v4 where we now completely get rid of kexec_mutex.

o Patch 1 makes sure all kexec_mutex acquisitions are trylocks. This prevents
  having to add any while(atomic_cmpxchg()) loops which I'd really hate to see
  here. If that can't be done then I think we're better off with the combined
  mutex+atomic var approach.
o Patch 2 does the mutex -> atomic var switch.

Revisions
=========

v3 -> v4
++++++++

o Someone forgot to Cc LKML on v3...

v2 -> v3
++++++++

o Dropped kexec_mutex entirely and made the atomic variable the one true lock
  for kexec (Eric)

v1 -> v2
++++++++

o Changed from Peterson-like synchronization to simpler atomic_cmpxchg
  (Petr)
o Slightly reworded changelog
o Added Fixes: tag. Technically should be up to since kexec can happen
  in an NMI, but that isn't such a clear target

Cheers,
Valentin

Valentin Schneider (2):
  kexec: Turn all kexec_mutex acquisitions into trylocks
  panic, kexec: Make __crash_kexec() NMI safe

 include/linux/kexec.h   |  2 +-
 kernel/kexec.c          | 11 ++++-------
 kernel/kexec_core.c     | 28 ++++++++++++++++------------
 kernel/kexec_file.c     |  4 ++--
 kernel/kexec_internal.h | 15 ++++++++++++++-
 kernel/ksysfs.c         |  7 ++++++-
 6 files changed, 43 insertions(+), 24 deletions(-)

--
2.31.1