From 4f09903078eeb9138cddce8db06100b82f8620e8 Mon Sep 17 00:00:00 2001 From: Sander Vanheule Date: Sat, 2 Jul 2022 18:08:27 +0200 Subject: [PATCH] cpumask: add UP optimised for_each_*_cpu versions On uniprocessor builds, the following loops will always run over a mask that contains one enabled CPU (cpu0): - for_each_possible_cpu - for_each_online_cpu - for_each_present_cpu Provide uniprocessor-specific macros for these loops, that always run exactly once. Link: https://lkml.kernel.org/r/3a92869b902a075b97be5d1452c9c6badbbff0df.1656777646.git.sander@svanheule.net Signed-off-by: Sander Vanheule Acked-by: Yury Norov Cc: Andy Shevchenko Cc: Borislav Petkov Cc: Dave Hansen Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Marco Elver Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Valentin Schneider Signed-off-by: Andrew Morton --- include/linux/cpumask.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index fe29ac7..5336127 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -811,9 +811,16 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS); /* First bits of cpu_bit_bitmap are in fact unset. */ #define cpu_none_mask to_cpumask(cpu_bit_bitmap[0]) +#if NR_CPUS == 1 +/* Uniprocessor: the possible/online/present masks are always "1" */ +#define for_each_possible_cpu(cpu) for ((cpu) = 0; (cpu) < 1; (cpu)++) +#define for_each_online_cpu(cpu) for ((cpu) = 0; (cpu) < 1; (cpu)++) +#define for_each_present_cpu(cpu) for ((cpu) = 0; (cpu) < 1; (cpu)++) +#else #define for_each_possible_cpu(cpu) for_each_cpu((cpu), cpu_possible_mask) #define for_each_online_cpu(cpu) for_each_cpu((cpu), cpu_online_mask) #define for_each_present_cpu(cpu) for_each_cpu((cpu), cpu_present_mask) +#endif /* Wrappers for arch boot code to manipulate normally-constant masks */ void init_cpu_present(const struct cpumask *src); -- 2.7.4