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Message-Id: <3a92869b902a075b97be5d1452c9c6badbbff0df.1656777646.git.sander@svanheule.net>
Date: Sat, 2 Jul 2022 18:08:27 +0200
From: Sander Vanheule <sander@...nheule.net>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
elver@...gle.com, gregkh@...uxfoundation.org,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>, vschneid@...hat.com,
Yury Norov <yury.norov@...il.com>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H . Peter Anvin" <hpa@...or.com>,
Sander Vanheule <sander@...nheule.net>
Subject: [PATCH v4 4/5] 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.
Signed-off-by: Sander Vanheule <sander@...nheule.net>
---
include/linux/cpumask.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 7fbef41b3093..6c5b4ee000f2 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -750,9 +750,16 @@ 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
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