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

0 files changed, 0 insertions, 0 deletions