stuartl/linux-stable
1
0
Fork 0
mirror of https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable.git synced 2025-09-26 17:10:55 +10:00
Code Issues Releases Wiki Activity
989,281 Commits 99 Branches 5,412 Tags 8.4 GiB
56314b90fd
Go to file
Valentin Schneider 56314b90fd panic, kexec: make __crash_kexec() NMI safe 
commit 05c6257433 upstream.

Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI
panic() doesn't work.  The cause of that lies in the PREEMPT_RT definition
of mutex_trylock():

	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
		return 0;

This prevents an nmi_panic() from executing the main body of
__crash_kexec() which does the actual kexec into the kdump kernel.  The
warning and return are explained by:

  6ce47fd961 ("rtmutex: Warn if trylock is called from hard/softirq context")
  [...]
  The reasons for this are:

      1) There is a potential deadlock in the slowpath

      2) Another cpu which blocks on the rtmutex will boost the task
	 which allegedly locked the rtmutex, but that cannot work
	 because the hard/softirq context borrows the task context.

Furthermore, grabbing the lock isn't NMI safe, so do away with kexec_mutex
and replace it with an atomic variable.  This is somewhat overzealous as
*some* callsites could keep using a mutex (e.g.  the sysfs-facing ones
like crash_shrink_memory()), but this has the benefit of involving a
single unified lock and preventing any future NMI-related surprises.

Tested by triggering NMI panics via:

  $ echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi
  $ echo 1 > /proc/sys/kernel/unknown_nmi_panic
  $ echo 1 > /proc/sys/kernel/panic

  $ ipmitool power diag

Link: https://lkml.kernel.org/r/20220630223258.4144112-3-vschneid@redhat.com
Fixes: 6ce47fd961 ("rtmutex: Warn if trylock is called from hard/softirq context")
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-04-20 12:10:29 +02:00
arch riscv: Handle zicsr/zifencei issues between clang and binutils 2023-04-20 12:10:28 +02:00
block
certs
crypto asymmetric_keys: log on fatal failures in PE/pkcs7 2023-04-20 12:10:27 +02:00
Documentation powerpc/pseries: Add support for FORM2 associativity 2023-04-20 12:10:28 +02:00
drivers coresight-etm4: Fix for() loop drvdata->nr_addr_cmp range bug 2023-04-20 12:10:28 +02:00
fs sysctl: add proc_dou8vec_minmax() 2023-04-20 12:10:26 +02:00
include kexec: turn all kexec_mutex acquisitions into trylocks 2023-04-20 12:10:29 +02:00
init kbuild: check the minimum assembler version in Kconfig 2023-04-20 12:10:28 +02:00
io_uring
ipc
kernel panic, kexec: make __crash_kexec() NMI safe 2023-04-20 12:10:29 +02:00
lib
LICENSES
mm mm/swap: fix swap_info_struct race between swapoff and get_swap_pages() 2023-04-20 12:10:24 +02:00
net udp6: fix potential access to stale information 2023-04-20 12:10:26 +02:00
samples
scripts kbuild: Switch to 'f' variants of integrated assembler flag 2023-04-20 12:10:28 +02:00
security keys: Do not cache key in task struct if key is requested from kernel thread 2023-04-05 11:23:34 +02:00
sound ALSA: hda/sigmatel: fix S/PDIF out on Intel D*45* motherboards 2023-04-20 12:10:25 +02:00
tools libbpf: Fix single-line struct definition output in btf_dump 2023-04-20 12:10:26 +02:00
usr
virt KVM: fix memoryleak in kvm_init() 2023-04-05 11:23:43 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile kbuild: check CONFIG_AS_IS_LLVM instead of LLVM_IAS 2023-04-20 12:10:28 +02:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.