Commit b1fcf9b8 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

rcu: Provide __rcu_is_watching() 



Same as rcu_is_watching() but without the preempt_disable/enable() pair
inside the function. It is merked noinstr so it ends up in the
non-instrumentable text section.

This is useful for non-preemptible code especially in the low level entry
section. Using rcu_is_watching() there results in a call to the
preempt_schedule_notrace() thunk which triggers noinstr section warnings in
objtool.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200512213810.518709291@linutronix.de
parent 8ae0ae67

include/linux/rcutiny.h

+1 −0
Original line number Diff line number Diff line
@@ -86,6 +86,7 @@ static inline void rcu_scheduler_starting(void) { } 
static inline void rcu_end_inkernel_boot(void) { }

static inline bool rcu_inkernel_boot_has_ended(void) { return true; }

static inline bool rcu_is_watching(void) { return true; }

static inline bool __rcu_is_watching(void) { return true; }

static inline void rcu_momentary_dyntick_idle(void) { }

static inline void kfree_rcu_scheduler_running(void) { }

static inline bool rcu_gp_might_be_stalled(void) { return false; }

include/linux/rcutree.h

+1 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ extern int rcu_scheduler_active __read_mostly; 
void rcu_end_inkernel_boot(void);

bool rcu_inkernel_boot_has_ended(void);

bool rcu_is_watching(void);

bool __rcu_is_watching(void);

#ifndef CONFIG_PREEMPTION

void rcu_all_qs(void);

#endif

kernel/rcu/tree.c

+5 −0
Original line number Diff line number Diff line
@@ -985,6 +985,11 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp) 
	}

}



noinstr bool __rcu_is_watching(void)

{

	return !rcu_dynticks_curr_cpu_in_eqs();

}



/**

 * rcu_is_watching - see if RCU thinks that the current CPU is not idle

 *

CRA Git | Maintained and supported by SUSTech CRA and CCSE