diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/bits.h | 5 | ||||
| -rw-r--r-- | include/linux/compiler.h | 22 | ||||
| -rw-r--r-- | include/linux/cpumask.h | 9 |
3 files changed, 28 insertions, 8 deletions
diff --git a/include/linux/bits.h b/include/linux/bits.h index 60044b608817..61a75d3f294b 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -20,9 +20,8 @@ */ #if !defined(__ASSEMBLY__) #include <linux/build_bug.h> -#define GENMASK_INPUT_CHECK(h, l) \ - (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ - __is_constexpr((l) > (h)), (l) > (h), 0))) +#include <linux/compiler.h> +#define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h))) #else /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, diff --git a/include/linux/compiler.h b/include/linux/compiler.h index efd43df3a99a..b087de2f3e94 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -308,6 +308,28 @@ static inline void *offset_to_ptr(const int *off) #define statically_true(x) (__builtin_constant_p(x) && (x)) /* + * Similar to statically_true() but produces a constant expression + * + * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(), + * which require their input to be a constant expression and for which + * statically_true() would otherwise fail. + * + * This is a trade-off: const_true() requires all its operands to be + * compile time constants. Else, it would always returns false even on + * the most trivial cases like: + * + * true || non_const_var + * + * On the opposite, statically_true() is able to fold more complex + * tautologies and will return true on expressions such as: + * + * !(non_const_var * 8 % 4) + * + * For the general case, statically_true() is better. + */ +#define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false) + +/* * This is needed in functions which generate the stack canary, see * arch/x86/kernel/smpboot.c::start_secondary() for an example. */ diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 9278a50d514f..36a890d0dd57 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -391,7 +391,7 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta for_each_set_bit_from(cpu, cpumask_bits(mask), small_cpumask_bits) /** - * cpumask_any_but - return a "random" in a cpumask, but not this one. + * cpumask_any_but - return an arbitrary cpu in a cpumask, but not this one. * @mask: the cpumask to search * @cpu: the cpu to ignore. * @@ -411,7 +411,7 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu) } /** - * cpumask_any_and_but - pick a "random" cpu from *mask1 & *mask2, but not this one. + * cpumask_any_and_but - pick an arbitrary cpu from *mask1 & *mask2, but not this one. * @mask1: the first input cpumask * @mask2: the second input cpumask * @cpu: the cpu to ignore @@ -840,7 +840,7 @@ void cpumask_copy(struct cpumask *dstp, const struct cpumask *srcp) } /** - * cpumask_any - pick a "random" cpu from *srcp + * cpumask_any - pick an arbitrary cpu from *srcp * @srcp: the input cpumask * * Return: >= nr_cpu_ids if no cpus set. @@ -848,7 +848,7 @@ void cpumask_copy(struct cpumask *dstp, const struct cpumask *srcp) #define cpumask_any(srcp) cpumask_first(srcp) /** - * cpumask_any_and - pick a "random" cpu from *mask1 & *mask2 + * cpumask_any_and - pick an arbitrary cpu from *mask1 & *mask2 * @mask1: the first input cpumask * @mask2: the second input cpumask * @@ -1043,7 +1043,6 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS); /* Wrappers for arch boot code to manipulate normally-constant masks */ void init_cpu_present(const struct cpumask *src); void init_cpu_possible(const struct cpumask *src); -void init_cpu_online(const struct cpumask *src); #define assign_cpu(cpu, mask, val) \ assign_bit(cpumask_check(cpu), cpumask_bits(mask), (val)) |