Add missing kernel-doc comments and rearrange the order of others to
prevent all kernel-doc warnings.

 - add function Returns: sections or format existing comments as kernel-doc
 - add missing function parameter comments
 - use "/**" for smp_call_function_any() and on_each_cpu_cond_mask()
 - correct the commented function name for on_each_cpu_cond_mask()
 - use correct format for function short descriptions
 - add all kernel-doc comments for smp_call_on_cpu()
 - remove kernel-doc comments for raw_smp_processor_id() since there is
   no prototype for it here (other than !SMP)
 - in smp.h, rearrange some lines so that the kernel-doc comments for
   smp_processor_id() are immediately before the macro (to prevent
   kernel-doc warnings)
 - remove "Returns" from smp_call_function() since it doesn't
   return a value

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260310061726.1153764-1-rdunlap@infradead.org

Some platforms require panic handling to execute on a specific CPU for
crash dump to work reliably.  This can be due to firmware limitations,
interrupt routing constraints, or platform-specific requirements where
only a single CPU is able to safely enter the crash kernel.

Add the panic_force_cpu= kernel command-line parameter to redirect panic
execution to a designated CPU.  When the parameter is provided, the CPU
that initially triggers panic forwards the panic context to the target CPU
via IPI, which then proceeds with the normal panic and kexec flow.

The IPI delivery is implemented as a weak function
(panic_smp_redirect_cpu) so architectures with NMI support can override it
for more reliable delivery.

If the specified CPU is invalid, offline, or a panic is already in
progress on another CPU, the redirection is skipped and panic continues on
the current CPU.

[pnina.feder@mobileye.com: fix unused variable warning]
  Link: https://lkml.kernel.org/r/20260126122618.2967950-1-pnina.feder@mobileye.com
Link: https://lkml.kernel.org/r/20260122102457.1154599-1-pnina.feder@mobileye.com
Signed-off-by: Pnina Feder <pnina.feder@mobileye.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

When governors used during cpuidle try to find the most optimal idle state
for a CPU or a group of CPUs, they are known to quite often fail. One
reason for this is, that they are not taking into account whether there has
been an IPI scheduled for any of the CPUs that are affected by the selected
idle state.

To enable pending IPIs to be taken into account for cpuidle decisions,
introduce a new helper function, cpus_peek_for_pending_ipi().

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Pull smp updates from Thomas Gleixner:
 "A set of updates for SMP function calls:

   - Improve locality of smp_call_function_any() by utilizing
     sched_numa_find_nth_cpu() instead of picking a random CPU

   - Wait for work completion in smp_call_function_many_cond() only when
     there was actually work enqueued

   - Simplify functions by unutlizing the appropriate cpumask_*()
     interfaces

   - Trivial cleanups"

* tag 'smp-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Wait only if work was enqueued
  smp: Defer check for local execution in smp_call_function_many_cond()
  smp: Use cpumask_any_but() in smp_call_function_many_cond()
  smp: Improve locality in smp_call_function_any()
  smp: Fix typo in comment for raw_smp_processor_id()

GCC appears to have kind of fragile inlining heuristics, in the
sense that it can change whether or not it inlines something based on
optimizations. It looks like the kcov instrumentation being added (or in
this case, removed) from a function changes the optimization results,
and some functions marked "inline" are _not_ inlined. In that case,
we end up with __init code calling a function not marked __init, and we
get the build warnings I'm trying to eliminate in the coming patch that
adds __no_sanitize_coverage to __init functions:

WARNING: modpost: vmlinux: section mismatch in reference: xbc_exit+0x8 (section: .text.unlikely) -> _xbc_exit (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: real_mode_size_needed+0x15 (section: .text.unlikely) -> real_mode_blob_end (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: __set_percpu_decrypted+0x16 (section: .text.unlikely) -> early_set_memory_decrypted (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: memblock_alloc_from+0x26 (section: .text.unlikely) -> memblock_alloc_try_nid (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_set_root_pointer+0xc (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_get_root_pointer+0x8 (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: efi_config_table_is_usable+0x16 (section: .text.unlikely) -> xen_efi_config_table_is_usable (section: .init.text)

This problem is somewhat fragile (though using either __always_inline
or __init will deterministically solve it), but we've tripped over
this before with GCC and the solution has usually been to just use
__always_inline and move on.

For x86 this means forcing several functions to be inline with
__always_inline.

Link: https://lore.kernel.org/r/20250724055029.3623499-2-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

The comment in `smp.h` incorrectly refers to `raw_processor_id()`
instead of the correct function name `raw_smp_processor_id()`.

Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/all/d096779819962c305b85cd12bda41b593e0981aa.1749536622.git.viresh.kumar@linaro.org

Pull RCU updates from Neeraj Upadhyay:
 "Context tracking:
   - rename context tracking state related symbols and remove references
     to "dynticks" in various context tracking state variables and
     related helpers
   - force context_tracking_enabled_this_cpu() to be inlined to avoid
     leaving a noinstr section

  CSD lock:
   - enhance CSD-lock diagnostic reports
   - add an API to provide an indication of ongoing CSD-lock stall

  nocb:
   - update and simplify RCU nocb code to handle (de-)offloading of
     callbacks only for offline CPUs
   - fix RT throttling hrtimer being armed from offline CPU

  rcutorture:
   - remove redundant rcu_torture_ops get_gp_completed fields
   - add SRCU ->same_gp_state and ->get_comp_state functions
   - add generic test for NUM_ACTIVE_*RCU_POLL* for testing RCU and SRCU
     polled grace periods
   - add CFcommon.arch for arch-specific Kconfig options
   - print number of update types in rcu_torture_write_types()
   - add rcutree.nohz_full_patience_delay testing to the TREE07 scenario
   - add a stall_cpu_repeat module parameter to test repeated CPU stalls
   - add argument to limit number of CPUs a guest OS can use in
     torture.sh

  rcustall:
   - abbreviate RCU CPU stall warnings during CSD-lock stalls
   - Allow dump_cpu_task() to be called without disabling preemption
   - defer printing stall-warning backtrace when holding rcu_node lock

  srcu:
   - make SRCU gp seq wrap-around faster
   - add KCSAN checks for concurrent updates to ->srcu_n_exp_nodelay and
     ->reschedule_count which are used in heuristics governing
     auto-expediting of normal SRCU grace periods and
     grace-period-state-machine delays
   - mark idle SRCU-barrier callbacks to help identify stuck
     SRCU-barrier callback

  rcu tasks:
   - remove RCU Tasks Rude asynchronous APIs as they are no longer used
   - stop testing RCU Tasks Rude asynchronous APIs
   - fix access to non-existent percpu regions
   - check processor-ID assumptions during chosen CPU calculation for
     callback enqueuing
   - update description of rtp->tasks_gp_seq grace-period sequence
     number
   - add rcu_barrier_cb_is_done() to identify whether a given
     rcu_barrier callback is stuck
   - mark idle Tasks-RCU-barrier callbacks
   - add *torture_stats_print() functions to print detailed diagnostics
     for Tasks-RCU variants
   - capture start time of rcu_barrier_tasks*() operation to help
     distinguish a hung barrier operation from a long series of barrier
     operations

  refscale:
   - add a TINY scenario to support tests of Tiny RCU and Tiny
     SRCU
   - optimize process_durations() operation

  rcuscale:
   - dump stacks of stalled rcu_scale_writer() instances and
     grace-period statistics when rcu_scale_writer() stalls
   - mark idle RCU-barrier callbacks to identify stuck RCU-barrier
     callbacks
   - print detailed grace-period and barrier diagnostics on
     rcu_scale_writer() hangs for Tasks-RCU variants
   - warn if async module parameter is specified for RCU implementations
     that do not have async primitives such as RCU Tasks Rude
   - make all writer tasks report upon hang
   - tolerate repeated GFP_KERNEL failure in rcu_scale_writer()
   - use special allocator for rcu_scale_writer()
   - NULL out top-level pointers to heap memory to avoid double-free
     bugs on modprobe failures
   - maintain per-task instead of per-CPU callbacks count to avoid any
     issues with migration of either tasks or callbacks
   - constify struct ref_scale_ops

  Fixes:
   - use system_unbound_wq for kfree_rcu work to avoid disturbing
     isolated CPUs

  Misc:
   - warn on unexpected rcu_state.srs_done_tail state
   - better define "atomic" for list_replace_rcu() and
     hlist_replace_rcu() routines
   - annotate struct kvfree_rcu_bulk_data with __counted_by()"

* tag 'rcu.release.v6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (90 commits)
  rcu: Defer printing stall-warning backtrace when holding rcu_node lock
  rcu/nocb: Remove superfluous memory barrier after bypass enqueue
  rcu/nocb: Conditionally wake up rcuo if not already waiting on GP
  rcu/nocb: Fix RT throttling hrtimer armed from offline CPU
  rcu/nocb: Simplify (de-)offloading state machine
  context_tracking: Tag context_tracking_enabled_this_cpu() __always_inline
  context_tracking, rcu: Rename rcu_dyntick trace event into rcu_watching
  rcu: Update stray documentation references to rcu_dynticks_eqs_{enter, exit}()
  rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()
  rcu: Rename rcu_implicit_dynticks_qs() into rcu_watching_snap_recheck()
  rcu: Rename dyntick_save_progress_counter() into rcu_watching_snap_save()
  rcu: Rename struct rcu_data .exp_dynticks_snap into .exp_watching_snap
  rcu: Rename struct rcu_data .dynticks_snap into .watching_snap
  rcu: Rename rcu_dynticks_zero_in_eqs() into rcu_watching_zero_in_eqs()
  rcu: Rename rcu_dynticks_in_eqs_since() into rcu_watching_snap_stopped_since()
  rcu: Rename rcu_dynticks_in_eqs() into rcu_watching_snap_in_eqs()
  rcu: Rename rcu_dynticks_eqs_online() into rcu_watching_online()
  context_tracking, rcu: Rename rcu_dynticks_curr_cpu_in_eqs() into rcu_is_watching_curr_cpu()
  context_tracking, rcu: Rename rcu_dynticks_task*() into rcu_task*()
  refscale: Constify struct ref_scale_ops
  ...

smp_prepare_boot_cpu() is only called during boot, hence mark it as
__init.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/all/20240907082720.452148-1-maobibo@loongson.cn

If a CSD-lock stall goes on long enough, it will cause an RCU CPU
stall warning.  This additional warning provides much additional
console-log traffic and little additional information.  Therefore,
provide a new csd_lock_is_stuck() function that returns true if there
is an ongoing CSD-lock stall.  This function will be used by the RCU
CPU stall warnings to provide a one-line indication of the stall when
this function returns true.

[ neeraj.upadhyay: Apply Rik van Riel feedback. ]
[ neeraj.upadhyay: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Leonardo Bras <leobras@redhat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>

Pull x86 cleanups from Ingo Molnar:
 "Misc cleanups, including a large series from Thomas Gleixner to cure
  sparse warnings"

* tag 'x86-cleanups-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi: Drop unused declaration of proc_nmi_enabled()
  x86/callthunks: Use EXPORT_PER_CPU_SYMBOL_GPL() for per CPU variables
  x86/cpu: Provide a declaration for itlb_multihit_kvm_mitigation
  x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_current
  x86/uaccess: Add missing __force to casts in __access_ok() and valid_user_address()
  x86/percpu: Cure per CPU madness on UP
  smp: Consolidate smp_prepare_boot_cpu()
  x86/msr: Add missing __percpu annotations
  x86/msr: Prepare for including <linux/percpu.h> into <asm/msr.h>
  perf/x86/amd/uncore: Fix __percpu annotation
  x86/nmi: Remove an unnecessary IS_ENABLED(CONFIG_SMP)
  x86/apm_32: Remove dead function apm_get_battery_status()
  x86/insn-eval: Fix function param name in get_eff_addr_sib()