diff options
| author | Yury Norov <ynorov@nvidia.com> | 2026-07-28 22:23:54 -0400 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-07-31 12:35:26 +0200 |
| commit | 5186ef36909c792591fda7a1ae2afc168f60bc90 (patch) | |
| tree | d615497fec4fc90fc17dddc4538e1d44f9f60ee0 /kernel/stop_machine.c | |
| parent | 04998aa54848f15332202d0bea008d2ca1ed1713 (diff) | |
stop_machine: Make stop_one_cpu_nowait() return void
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 <ynorov@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Bradley Morgan <include@grrlz.net>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://patch.msgid.link/20260729022355.325058-1-ynorov@nvidia.com
Diffstat (limited to 'kernel/stop_machine.c')
| -rw-r--r-- | kernel/stop_machine.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 773d8e9ae30c..d085ba1f4b44 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -7,6 +7,7 @@ * Copyright (C) 2010 SUSE Linux Products GmbH * Copyright (C) 2010 Tejun Heo <tj@kernel.org> */ +#include <linux/bug.h> #include <linux/compiler.h> #include <linux/completion.h> #include <linux/cpu.h> @@ -376,17 +377,14 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * * and will remain untouched until stopper starts executing @fn. * * CONTEXT: - * Don't care. - * - * RETURNS: - * true if cpu_stop_work was queued successfully and @fn will be called, - * false otherwise. + * Don't care, but the caller must ensure @cpu's stopper stays enabled + * until the work is queued, e.g. by preempt_disable(). */ -bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, - struct cpu_stop_work *work_buf) +void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, + struct cpu_stop_work *work_buf) { *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, .caller = _RET_IP_, }; - return cpu_stop_queue_work(cpu, work_buf); + WARN_ON_ONCE(!cpu_stop_queue_work(cpu, work_buf)); } static bool queue_stop_cpus_work(const struct cpumask *cpumask, |