lkml.org 
[lkml]   [2022]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 3/4] cpumask: Add UP optimised for_each_*_cpu versions
Date
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.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
---
include/linux/cpumask.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d6add0e29ef4..7ccddbc27ac3 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -731,9 +731,16 @@ 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);
--
2.36.1
\
 
 \ /
  Last update: 2022-06-05 08:24    [W:0.491 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site