From 0e985e9d22864e29d5d2b3d909ad15134d7f6d46 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 12 Jan 2023 20:44:04 +0100 Subject: cpuidle: Add comments about noinstr/__cpuidle usage Add a few words on noinstr / __cpuidle usage. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230112195542.397238052@infradead.org --- include/linux/compiler_types.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index d7858901f035..dea5bf5bd09c 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -239,6 +239,16 @@ struct ftrace_likely_data { #define noinstr __noinstr_section(".noinstr.text") +/* + * The __cpuidle section is used twofold: + * + * 1) the original use -- identifying if a CPU is 'stuck' in idle state based + * on it's instruction pointer. See cpu_in_idle(). + * + * 2) supressing instrumentation around where cpuidle disables RCU; where the + * function isn't strictly required for #1, this is interchangeable with + * noinstr. + */ #define __cpuidle __noinstr_section(".cpuidle.text") #endif /* __KERNEL__ */ -- cgit v1.2.3