linux.git/kernel/panic.c, branch v6.18.21

panic: only warn about deprecated panic_print on write access

2026-01-30T09:32:22+00:00

commit 90f3c123247e9564f2ecf861946ec41ceaf5e198 upstream.

The panic_print_deprecated() warning is being triggered on both read and
write operations to the panic_print parameter.

This causes spurious warnings when users run 'sysctl -a' to list all
sysctl values, since that command reads /proc/sys/kernel/panic_print and
triggers the deprecation notice.

Modify the handlers to only emit the deprecation warning when the
parameter is actually being set:

 - sysctl_panic_print_handler(): check 'write' flag before warning.
 - panic_print_get(): remove the deprecation call entirely.

This way, users are only warned when they actively try to use the
deprecated parameter, not when passively querying system state.

Link: https://lkml.kernel.org/r/20260106163321.83586-1-gal@nvidia.com
Fixes: ee13240cd78b ("panic: add note that panic_print sysctl interface is deprecated")
Fixes: 2683df6539cb ("panic: add note that 'panic_print' parameter is deprecated")
Signed-off-by: Gal Pressman 
Reviewed-by: Mark Bloch 
Reviewed-by: Nimrod Oren 
Cc: Feng Tang 
Cc: Joel Granados 
Cc: Petr Mladek 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

panic: remove CONFIG_PANIC_ON_OOPS_VALUE

2025-09-28T18:36:13+00:00

There's really no need for this since it's 0 or 1 when
CONFIG_PANIC_ON_OOPS is disabled/enabled, so just use IS_ENABLED()
instead.  The extra symbol goes back to the original code adding it in
commit 2a01bb3885c9 ("panic: Make panic_on_oops configurable").

Link: https://lkml.kernel.org/r/20250924094303.18521-2-johannes@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Andrew Morton

panic: remove redundant panic-cpu backtrace

2025-09-14T00:32:54+00:00

Backtraces from all CPUs are printed during panic() when
SYS_INFO_ALL_CPU_BT is set.  It shows the backtrace for the panic-CPU even
when it has already been explicitly printed before.

Do not change the legacy code which prints the backtrace in various
contexts, for example, as part of Oops report, right after panic message. 
It will always be visible in the crash dump.

Instead, remember when the backtrace was printed, and skip it when dumping
the optional backtraces on all CPUs.

[akpm@linux-foundation.org: make panic_this_cpu_backtrace_printed static]
  Closes: https://lore.kernel.org/oe-kbuild-all/202509050048.FMpVvh1u-lkp@intel.com/
[pmladek@suse.com: Handle situations when the backtrace was not printed for the panic CPU]
Link: https://lkml.kernel.org/r/20250903100418.410026-1-pmladek@suse.com
Signed-off-by: Sergey Senozhatsky 
Link: https://lore.kernel.org/r/20250731030314.3818040-1-senozhatsky@chromium.org
Signed-off-by: Petr Mladek 
Tested-by: Feng Tang 
Reviewed-by: John Ogness 
Signed-off-by: Andrew Morton

panic/printk: replace this_cpu_in_panic() with panic_on_this_cpu()

2025-09-14T00:32:52+00:00

The helper this_cpu_in_panic() duplicated logic already provided by
panic_on_this_cpu().

Remove this_cpu_in_panic() and switch all users to panic_on_this_cpu().

This simplifies the code and avoids having two helpers for the same check.

Link: https://lkml.kernel.org/r/20250825022947.1596226-8-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang 
Cc: Anna Schumaker 
Cc: Baoquan He 
Cc: "Darrick J. Wong" 
Cc: Dave Young 
Cc: Doug Anderson 
Cc: "Guilherme G. Piccoli" 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: John Ogness 
Cc: Kees Cook 
Cc: Li Huafei 
Cc: "Luck, Tony" 
Cc: Luo Gengkun 
Cc: Max Kellermann 
Cc: Nam Cao 
Cc: oushixiong 
Cc: Petr Mladek 
Cc: Qianqiang Liu 
Cc: Sergey Senozhatsky 
Cc: Sohil Mehta 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Zimemrmann 
Cc: Thorsten Blum 
Cc: Ville Syrjala 
Cc: Vivek Goyal 
Cc: Yicong Yang 
Cc: Yunhui Cui 
Cc: Yury Norov (NVIDIA) 
Signed-off-by: Andrew Morton

panic: use panic_try_start() in vpanic()

2025-09-14T00:32:52+00:00

vpanic() had open-coded logic to claim panic_cpu with atomic_try_cmpxchg. 
This is already handled by panic_try_start().

Switch to panic_try_start() and use panic_on_other_cpu() for the fallback
path.

This removes duplicate code and makes panic handling consistent across
functions.

Link: https://lkml.kernel.org/r/20250825022947.1596226-6-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang 
Cc: Anna Schumaker 
Cc: Baoquan He 
Cc: "Darrick J. Wong" 
Cc: Dave Young 
Cc: Doug Anderson 
Cc: "Guilherme G. Piccoli" 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: John Ogness 
Cc: Kees Cook 
Cc: Li Huafei 
Cc: "Luck, Tony" 
Cc: Luo Gengkun 
Cc: Max Kellermann 
Cc: Nam Cao 
Cc: oushixiong 
Cc: Petr Mladek 
Cc: Qianqiang Liu 
Cc: Sergey Senozhatsky 
Cc: Sohil Mehta 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Zimemrmann 
Cc: Thorsten Blum 
Cc: Ville Syrjala 
Cc: Vivek Goyal 
Cc: Yicong Yang 
Cc: Yunhui Cui 
Cc: Yury Norov (NVIDIA) 
Signed-off-by: Andrew Morton

panic: use panic_try_start() in nmi_panic()

2025-09-14T00:32:51+00:00

nmi_panic() duplicated the logic to claim panic_cpu with
atomic_try_cmpxchg.  This is already wrapped in panic_try_start().

Replace the open-coded logic with panic_try_start(), and use
panic_on_other_cpu() for the fallback path.

This removes duplication and keeps panic handling code consistent.

Link: https://lkml.kernel.org/r/20250825022947.1596226-5-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang 
Cc: Anna Schumaker 
Cc: Baoquan He 
Cc: "Darrick J. Wong" 
Cc: Dave Young 
Cc: Doug Anderson 
Cc: "Guilherme G. Piccoli" 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: John Ogness 
Cc: Kees Cook 
Cc: Li Huafei 
Cc: "Luck, Tony" 
Cc: Luo Gengkun 
Cc: Max Kellermann 
Cc: Nam Cao 
Cc: oushixiong 
Cc: Petr Mladek 
Cc: Qianqiang Liu 
Cc: Sergey Senozhatsky 
Cc: Sohil Mehta 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Zimemrmann 
Cc: Thorsten Blum 
Cc: Ville Syrjala 
Cc: Vivek Goyal 
Cc: Yicong Yang 
Cc: Yunhui Cui 
Cc: Yury Norov (NVIDIA) 
Signed-off-by: Andrew Morton

panic: introduce helper functions for panic state

2025-09-14T00:32:51+00:00

Patch series "panic: introduce panic status function family", v2.

This series introduces a family of helper functions to manage panic state
and updates existing code to use them.

Before this series, panic state helpers were scattered and inconsistent. 
For example, panic_in_progress() was defined in printk/printk.c, not in
panic.c or panic.h.  As a result, developers had to look in unexpected
places to understand or re-use panic state logic.  Other checks were open-
coded, duplicating logic across panic, crash, and watchdog paths.

The new helpers centralize the functionality in panic.c/panic.h:
  - panic_try_start()
  - panic_reset()
  - panic_in_progress()
  - panic_on_this_cpu()
  - panic_on_other_cpu()

Patches 1–8 add the helpers and convert panic/crash and printk/nbcon
code to use them.

Patch 9 fixes a bug in the watchdog subsystem by skipping checks when a
panic is in progress, avoiding interference with the panic CPU.

Together, this makes panic state handling simpler, more discoverable, and
more robust.


This patch (of 9):

This patch introduces four new helper functions to abstract the management
of the panic_cpu variable.  These functions will be used in subsequent
patches to refactor existing code.

The direct use of panic_cpu can be error-prone and ambiguous, as it
requires manual checks to determine which CPU is handling the panic.  The
new helpers clarify intent:

panic_try_start():
Atomically sets the current CPU as the panicking CPU.

panic_reset():
Reset panic_cpu to PANIC_CPU_INVALID.

panic_in_progress():
Checks if a panic has been triggered.

panic_on_this_cpu():
Returns true if the current CPU is the panic originator.

panic_on_other_cpu():
Returns true if a panic is on another CPU.

This change lays the groundwork for improved code readability
and robustness in the panic handling subsystem.

Link: https://lkml.kernel.org/r/20250825022947.1596226-1-wangjinchao600@gmail.com
Link: https://lkml.kernel.org/r/20250825022947.1596226-2-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang 
Cc: Anna Schumaker 
Cc: Baoquan He 
Cc: "Darrick J. Wong" 
Cc: Dave Young 
Cc: Doug Anderson 
Cc: "Guilherme G. Piccoli" 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: John Ogness 
Cc: Kees Cook 
Cc: Li Huafei 
Cc: "Luck, Tony" 
Cc: Luo Gengkun 
Cc: Max Kellermann 
Cc: Nam Cao 
Cc: oushixiong 
Cc: Petr Mladek 
Cc: Qianqiang Liu 
Cc: Sergey Senozhatsky 
Cc: Sohil Mehta 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Zimemrmann 
Cc: Thorsten Blum 
Cc: Ville Syrjala 
Cc: Vivek Goyal 
Cc: Yicong Yang 
Cc: Yunhui Cui 
Cc: Yury Norov (NVIDIA) b
Signed-off-by: Andrew Morton

panic: clean up message about deprecated 'panic_print' parameter

2025-09-14T00:32:50+00:00

Remove duplication of the message about deprecated 'panic_print'
parameter.

Also make the wording more direct.  Make it clear that the new parameters
already exist and should be used instead.

Link: https://lkml.kernel.org/r/20250825025701.81921-5-feng.tang@linux.alibaba.com
Signed-off-by: Petr Mladek 
Signed-off-by: Feng Tang 
Reviewed-by: Lance Yang 
Tested-by: Lance Yang 
Reviewed-by: Feng Tang 
Cc: Askar Safin 
Cc: John Ogness 
Cc: Jonathan Corbet 
Cc: "Paul E . McKenney" 
Cc: Steven Rostedt 
Signed-off-by: Andrew Morton

panic: add note that 'panic_print' parameter is deprecated

2025-09-14T00:32:50+00:00

Just like for 'panic_print's systcl interface, add similar note for setup
of kernel cmdline parameter and parameter under /sys/module/kernel/.

Also add __core_param_cb() macro, which enables to add special get/set
operation for a kernel parameter.

Link: https://lkml.kernel.org/r/20250825025701.81921-4-feng.tang@linux.alibaba.com
Signed-off-by: Feng Tang 
Suggested-by: Petr Mladek 
Reviewed-by: Petr Mladek 
Cc: Askar Safin 
Cc: John Ogness 
Cc: Jonathan Corbet 
Cc: Lance Yang 
Cc: "Paul E . McKenney" 
Cc: Steven Rostedt 
Signed-off-by: Andrew Morton

Merge tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-08-03T23:23:09+00:00

Pull non-MM updates from Andrew Morton:
 "Significant patch series in this pull request:

   - "squashfs: Remove page->mapping references" (Matthew Wilcox) gets
     us closer to being able to remove page->mapping

   - "relayfs: misc changes" (Jason Xing) does some maintenance and
     minor feature addition work in relayfs

   - "kdump: crashkernel reservation from CMA" (Jiri Bohac) switches
     us from static preallocation of the kdump crashkernel's working
     memory over to dynamic allocation. So the difficulty of a-priori
     estimation of the second kernel's needs is removed and the first
     kernel obtains extra memory

   - "generalize panic_print's dump function to be used by other
     kernel parts" (Feng Tang) implements some consolidation and
     rationalization of the various ways in which a failing kernel
     splats information at the operator

* tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (80 commits)
  tools/getdelays: add backward compatibility for taskstats version
  kho: add test for kexec handover
  delaytop: enhance error logging and add PSI feature description
  samples: Kconfig: fix spelling mistake "instancess" -> "instances"
  fat: fix too many log in fat_chain_add()
  scripts/spelling.txt: add notifer||notifier to spelling.txt
  xen/xenbus: fix typo "notifer"
  net: mvneta: fix typo "notifer"
  drm/xe: fix typo "notifer"
  cxl: mce: fix typo "notifer"
  KVM: x86: fix typo "notifer"
  MAINTAINERS: add maintainers for delaytop
  ucount: use atomic_long_try_cmpxchg() in atomic_long_inc_below()
  ucount: fix atomic_long_inc_below() argument type
  kexec: enable CMA based contiguous allocation
  stackdepot: make max number of pools boot-time configurable
  lib/xxhash: remove unused functions
  init/Kconfig: restore CONFIG_BROKEN help text
  lib/raid6: update recov_rvv.c zero page usage
  docs: update docs after introducing delaytop
  ...