[PATCH v1 2/3] lib/cpumask: add inline cpumask_next_wrap() for UP
From: Sander Vanheule
Date: Tue Aug 09 2022 - 13:37:11 EST
In the uniprocessor case, cpumask_next_wrap() can be simplified, as the
number of valid argument combinations is limited:
- 'start' can only be 0
- 'n' can only be -1 or 0
The only valid CPU that can then be returned, if any, will be the first
one set in the provided 'mask'.
For NR_CPUS == 1, include/linux/cpumask.h now provides an inline
definition of cpumask_next_wrap(), which will conflict with the one
provided by lib/cpumask.c. Make building of lib/cpumask.o again depend
on CONFIG_SMP=y (i.e. NR_CPUS > 1) to avoid the re-definition.
Suggested-by: Yury Norov <yury.norov@xxxxxxxxx>
Signed-off-by: Sander Vanheule <sander@xxxxxxxxxxxxx>
---
include/linux/cpumask.h | 19 +++++++++++++++++++
lib/Makefile | 3 ++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d8c2a40f8beb..bd047864c7ac 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -262,7 +262,26 @@ unsigned int cpumask_next_and(int n, const struct cpumask *src1p,
(cpu) = cpumask_next_zero((cpu), (mask)), \
(cpu) < nr_cpu_ids;)
+#if NR_CPUS == 1
+static inline
+unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
+{
+ cpumask_check(start);
+ if (n != -1)
+ cpumask_check(n);
+
+ /*
+ * Return the first available CPU when wrapping, or when starting before cpu0,
+ * since there is only one valid option.
+ */
+ if (wrap && n >= 0)
+ return nr_cpumask_bits;
+
+ return cpumask_first(mask);
+}
+#else
unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
+#endif
/**
* for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location
diff --git a/lib/Makefile b/lib/Makefile
index c95212141928..5927d7fa0806 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -34,9 +34,10 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
is_single_threaded.o plist.o decompress.o kobject_uevent.o \
earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
nmi_backtrace.o win_minmax.o memcat_p.o \
- buildid.o cpumask.o
+ buildid.o
lib-$(CONFIG_PRINTK) += dump_stack.o
+lib-$(CONFIG_SMP) += cpumask.o
lib-y += kobject.o klist.o
obj-y += lockref.o
--
2.37.1