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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" Add a few words on noinstr / __cpuidle usage. Signed-off-by: Peter Zijlstra (Intel) --- drivers/cpuidle/cpuidle.c | 12 ++++++++++++ include/linux/compiler_types.h | 10 ++++++++++ 2 files changed, 22 insertions(+) --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -252,6 +252,18 @@ noinstr int cpuidle_enter_state(struct c instrumentation_begin(); } + /* + * NOTE!! + * + * For cpuidle_state::enter() methods that do *NOT* set + * CPUIDLE_FLAG_RCU_IDLE RCU will be disabled here and these functions + * must be marked either noinstr or __cpuidle. + * + * For cpuidle_state::enter() methods that *DO* set + * CPUIDLE_FLAG_RCU_IDLE this isn't required, but they must mark the + * function calling ct_cpuidle_enter() as noinstr/__cpuidle and all + * functions called within the RCU-idle region. + */ entered_state = target_state->enter(dev, drv, index); if (WARN_ONCE(!irqs_disabled(), "%ps leaked IRQ state", target_state->enter)) --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -233,6 +233,16 @@ 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__ */ _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization