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Commit 293e2421 authored by Boqun Feng's avatar Boqun Feng Committed by Paul E. McKenney
Browse files

rcu: Remove superfluous versions of rcu_read_lock_sched_held() 



Currently, we have four versions of rcu_read_lock_sched_held(), depending
on the combined choices on PREEMPT_COUNT and DEBUG_LOCK_ALLOC.  However,
there is an existing function preemptible() that already distinguishes
between the PREEMPT_COUNT=y and PREEMPT_COUNT=n cases, and allows these
four implementations to be consolidated down to two.

This commit therefore uses preemptible() to achieve this consolidation.

Note that there could be a small performance regression in the case
of CONFIG_DEBUG_LOCK_ALLOC=y && PREEMPT_COUNT=n.  However, given the
overhead associated with CONFIG_DEBUG_LOCK_ALLOC=y, this should be
down in the noise.

Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 8c7c4829

include/linux/rcupdate.h

+1 −16
Original line number Diff line number Diff line
@@ -508,14 +508,7 @@ int rcu_read_lock_bh_held(void); 
 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side

 * critical section unless it can prove otherwise.

 */

#ifdef CONFIG_PREEMPT_COUNT

int rcu_read_lock_sched_held(void);

#else /* #ifdef CONFIG_PREEMPT_COUNT */

static inline int rcu_read_lock_sched_held(void)

{

	return 1;

}

#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */



#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@@ -532,18 +525,10 @@ static inline int rcu_read_lock_bh_held(void) 
	return 1;

}



#ifdef CONFIG_PREEMPT_COUNT

static inline int rcu_read_lock_sched_held(void)

{

	return preempt_count() != 0 || irqs_disabled();

	return !preemptible();

}

#else /* #ifdef CONFIG_PREEMPT_COUNT */

static inline int rcu_read_lock_sched_held(void)

{

	return 1;

}

#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */



#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */



#ifdef CONFIG_PROVE_RCU

kernel/rcu/update.c

+2 −2
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ static int rcu_normal_after_boot; 
module_param(rcu_normal_after_boot, int, 0);

#endif /* #ifndef CONFIG_TINY_RCU */



#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)

#ifdef CONFIG_DEBUG_LOCK_ALLOC

/**

 * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?

 *
@@ -111,7 +111,7 @@ int rcu_read_lock_sched_held(void) 
		return 0;

	if (debug_locks)

		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);

	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();

	return lockdep_opinion || !preemptible();

}

EXPORT_SYMBOL(rcu_read_lock_sched_held);

#endif