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0485235b6e
smp_call_function_any() disables preemption across the entire operation: selecting a target CPU, enqueueing the IPI, and synchronously waiting for the remote CPU. smp_call_function_single() already re-enables preemption before the synchronous csd_lock_wait(), so callers of smp_call_function_any() should benefit from the same shorter preemption-disabled section. Simply removing get_cpu() and put_cpu() from smp_call_function_any() would leave the preemption disablement entirely to smp_call_function_single(). That opens a preemption window between selecting the remote CPU, for example via sched_numa_find_nth_cpu(), and dispatching the IPI in smp_call_function_single(). If the selected CPU is fully offlined in that window, smp_call_function_single() fails its cpu_online() check and returns -ENXIO to the caller, violating the guarantee that smp_call_function_any() executes on any online CPU in the mask. Move the remote CPU selection into a common __smp_call_function_single() helper. Keep the target CPU selection and IPI dispatch within the same preemption-disabled region, while still allowing the wait path to use the shorter preemption-disabled section provided by smp_call_function_single(). Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Tested-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://patch.msgid.link/20260709122933.4021501-4-zhouchuyi@bytedance.com
72 lines
1.5 KiB
72 lines
1.5 KiB