Commit 0e985e9d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

cpuidle: Add comments about noinstr/__cpuidle usage 



Add a few words on noinstr / __cpuidle usage.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.397238052@infradead.org
parent 26388a7c

drivers/cpuidle/cpuidle.c

+12 −0
Original line number Diff line number Diff line
@@ -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))

include/linux/compiler_types.h

+10 −0
Original line number Diff line number Diff line
@@ -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__ */