kernel/linux.git/include/linux/stop_machine.h, branch v7.3-rc1

stop_machine: Make stop_one_cpu_nowait() return void

2026-07-31T10:35:26+00:00

No caller checks the return value from stop_one_cpu_nowait(). All callers require the callback to run and arrange for the target CPU's stopper to remain enabled while queuing the work. In particular, commit f0498d2a54e7 ("sched: Fix stop_one_cpu_nowait() vs hotplug") added preemption protection to the scheduler callers so that queuing must succeed once the target CPU has been observed online. Therefore, a failure is an unrecoverable violation rather than a condition individual callers can recover from. Diagnose it with WARN_ON_ONCE() in stop_one_cpu_nowait(). A check in the common helper covers current and future callers consistently, while individual checks would duplicate the same non-recoverable handling at every call site. Make the function return void because there is no longer a meaningful result for callers to consume. On UP, warn if the supplied CPU is not the current CPU because the work cannot be scheduled in that case. Signed-off-by: Yury Norov Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Bradley Morgan Reviewed-by: Shrikanth Hegde Link: https://patch.msgid.link/20260729022355.325058-1-ynorov@nvidia.com

stop_machine: Fix the documentation for a NULL cpus argument

2026-03-03T23:35:51+00:00

A recent refactoring of the kernel-docs for stop machine changed the description of the cpus parameter from "NULL = any online cpu" to "NULL = run on each online CPU". However the callback is only executed on a single CPU, not all of them. The old wording was a bit ambiguous and could have been read both ways. Reword the documentation to be correct again and hopefully also clearer. Fixes: fc6f89dc7078 ("stop_machine: Improve kernel-doc function-header comments") Signed-off-by: Thomas Weißschuh Signed-off-by: Paul E. McKenney Reviewed-by: Sebastian Andrzej Siewior

stop_machine: Improve kernel-doc function-header comments

2025-07-17T19:10:56+00:00

Add more detail to the kernel-doc function-header comments for stop_machine(), stop_machine_cpuslocked(), and stop_core_cpuslocked(). Signed-off-by: Paul E. McKenney

cpumask: make core headers including cpumask_types.h where possible

2024-06-25T05:25:02+00:00

Now that cpumask types are split out to a separate smaller header, many frequently included core headers may switch to using it. Link: https://lkml.kernel.org/r/20240528005648.182376-7-yury.norov@gmail.com Signed-off-by: Yury Norov Cc: Amit Daniel Kachhap Cc: Anna-Maria Behnsen Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Dennis Zhou Cc: Frederic Weisbecker Cc: Johannes Weiner Cc: Juri Lelli Cc: Kees Cook Cc: Mathieu Desnoyers Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Rasmus Villemoes Cc: Tejun Heo Cc: Thomas Gleixner Cc: Ulf Hansson Cc: Vincent Guittot Cc: Viresh Kumar Cc: Yury Norov Signed-off-by: Andrew Morton

stop_machine: Add stop_core_cpuslocked() for per-core operations

2022-05-12T13:35:29+00:00

Hardware core level testing features require near simultaneous execution of WRMSR instructions on all threads of a core to initiate a test. Provide a customized cut down version of stop_machine_cpuslocked() that just operates on the threads of a single core. Suggested-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Tony Luck Reviewed-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220506225410.1652287-4-tony.luck@intel.com Signed-off-by: Hans de Goede

stop_machine: mark helpers __always_inline

2021-03-13T19:27:30+00:00

With clang-13, some functions only get partially inlined, with a specialized version referring to a global variable. This triggers a harmless build-time check for the intel-rng driver: WARNING: modpost: drivers/char/hw_random/intel-rng.o(.text+0xe): Section mismatch in reference from the function stop_machine() to the function .init.text:intel_rng_hw_init() The function stop_machine() references the function __init intel_rng_hw_init(). This is often because stop_machine lacks a __init annotation or the annotation of intel_rng_hw_init is wrong. In this instance, an easy workaround is to force the stop_machine() function to be inline, along with related interfaces that did not show the same behavior at the moment, but theoretically could. The combination of the two patches listed below triggers the behavior in clang-13, but individually these commits are correct. Link: https://lkml.kernel.org/r/20210225130153.1956990-1-arnd@kernel.org Fixes: fe5595c07400 ("stop_machine: Provide stop_machine_cpuslocked()") Fixes: ee527cd3a20c ("Use stop_machine_run in the Intel RNG driver") Signed-off-by: Arnd Bergmann Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Thomas Gleixner Cc: Sebastian Andrzej Siewior Cc: "Paul E. McKenney" Cc: Ingo Molnar Cc: Prarit Bhargava Cc: Daniel Bristot de Oliveira Cc: Peter Zijlstra Cc: Valentin Schneider Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

stop_machine: Add function and caller debug info

2020-11-10T17:38:57+00:00

Crashes in stop-machine are hard to connect to the calling code, add a little something to help with that. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Reviewed-by: Daniel Bristot de Oliveira Link: https://lkml.kernel.org/r/20201023102346.116513635@infradead.org

stop_machine: Make stop_cpus() static

2020-01-17T09:19:21+00:00

The function stop_cpus() is only used internally by the stop_machine for stop multiple cpus. Make it static. Signed-off-by: Yangtao Li Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20191228161912.24082-1-tiny.windzz@gmail.com

stop_machine: remove try_stop_cpus helper

2019-12-17T12:32:51+00:00

try_stop_cpus is not used after this: commit c190c3b16c0f ("rcu: Switch synchronize_sched_expedited() to stop_one_cpu()") So remove it. Signed-off-by: Yangtao Li Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20191214195107.26480-1-tiny.windzz@gmail.com

processor: get rid of cpu_relax_yield

2019-06-15T10:25:55+00:00

stop_machine is the only user left of cpu_relax_yield. Given that it now has special semantics which are tied to stop_machine introduce a weak stop_machine_yield function which architectures can override, and get rid of the generic cpu_relax_yield implementation. Acked-by: Peter Zijlstra (Intel) Acked-by: Thomas Gleixner Signed-off-by: Heiko Carstens