diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2023-01-12 20:44:04 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-01-13 11:48:18 +0100 |
| commit | 0e985e9d22864e29d5d2b3d909ad15134d7f6d46 (patch) | |
| tree | 710fbac5e48688b81dec48394c2007de459252ce | |
| parent | 26388a7c353f7b1d3fd8a6df6452fa9773193155 (diff) | |
cpuidle: Add comments about noinstr/__cpuidle usage
Add a few words on noinstr / __cpuidle usage.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.397238052@infradead.org
| -rw-r--r-- | drivers/cpuidle/cpuidle.c | 12 | ||||
| -rw-r--r-- | include/linux/compiler_types.h | 10 |
2 files changed, 22 insertions, 0 deletions
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 73f7d8b763c6..500d1720421e 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -252,6 +252,18 @@ noinstr int cpuidle_enter_state(struct cpuidle_device *dev, 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)) 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__ */ |