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Commit 0e5da22e authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Move __rcu_read_lock() and __rcu_read_unlock() to tree_plugin.h 



The __rcu_read_lock() and __rcu_read_unlock() functions were moved
to kernel/rcu/update.c in order to implement tiny preemptible RCU.
However, tiny preemptible RCU was removed from the kernel a long time
ago, so this commit belatedly moves them back into the only remaining
preemptible-RCU code.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: default avatarNicholas Piggin <npiggin@gmail.com>
parent c3442697

kernel/rcu/tree_plugin.h

+44 −0
Original line number Diff line number Diff line
@@ -383,6 +383,50 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) 
	return rnp->gp_tasks != NULL;

}



/*

 * Preemptible RCU implementation for rcu_read_lock().

 * Just increment ->rcu_read_lock_nesting, shared state will be updated

 * if we block.

 */

void __rcu_read_lock(void)

{

	current->rcu_read_lock_nesting++;

	barrier();  /* critical section after entry code. */

}

EXPORT_SYMBOL_GPL(__rcu_read_lock);



/*

 * Preemptible RCU implementation for rcu_read_unlock().

 * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost

 * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then

 * invoke rcu_read_unlock_special() to clean up after a context switch

 * in an RCU read-side critical section and other special cases.

 */

void __rcu_read_unlock(void)

{

	struct task_struct *t = current;



	if (t->rcu_read_lock_nesting != 1) {

		--t->rcu_read_lock_nesting;

	} else {

		barrier();  /* critical section before exit code. */

		t->rcu_read_lock_nesting = INT_MIN;

		barrier();  /* assign before ->rcu_read_unlock_special load */

		if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))

			rcu_read_unlock_special(t);

		barrier();  /* ->rcu_read_unlock_special load before assign */

		t->rcu_read_lock_nesting = 0;

	}

#ifdef CONFIG_PROVE_LOCKING

	{

		int rrln = READ_ONCE(t->rcu_read_lock_nesting);



		WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);

	}

#endif /* #ifdef CONFIG_PROVE_LOCKING */

}

EXPORT_SYMBOL_GPL(__rcu_read_unlock);



/*

 * Advance a ->blkd_tasks-list pointer to the next entry, instead

 * returning NULL if at the end of the list.

kernel/rcu/update.c

+0 −48
Original line number Diff line number Diff line
@@ -226,54 +226,6 @@ core_initcall(rcu_set_runtime_mode); 


#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */



#ifdef CONFIG_PREEMPT_RCU



/*

 * Preemptible RCU implementation for rcu_read_lock().

 * Just increment ->rcu_read_lock_nesting, shared state will be updated

 * if we block.

 */

void __rcu_read_lock(void)

{

	current->rcu_read_lock_nesting++;

	barrier();  /* critical section after entry code. */

}

EXPORT_SYMBOL_GPL(__rcu_read_lock);



/*

 * Preemptible RCU implementation for rcu_read_unlock().

 * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost

 * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then

 * invoke rcu_read_unlock_special() to clean up after a context switch

 * in an RCU read-side critical section and other special cases.

 */

void __rcu_read_unlock(void)

{

	struct task_struct *t = current;



	if (t->rcu_read_lock_nesting != 1) {

		--t->rcu_read_lock_nesting;

	} else {

		barrier();  /* critical section before exit code. */

		t->rcu_read_lock_nesting = INT_MIN;

		barrier();  /* assign before ->rcu_read_unlock_special load */

		if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))

			rcu_read_unlock_special(t);

		barrier();  /* ->rcu_read_unlock_special load before assign */

		t->rcu_read_lock_nesting = 0;

	}

#ifdef CONFIG_PROVE_LOCKING

	{

		int rrln = READ_ONCE(t->rcu_read_lock_nesting);



		WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);

	}

#endif /* #ifdef CONFIG_PROVE_LOCKING */

}

EXPORT_SYMBOL_GPL(__rcu_read_unlock);



#endif /* #ifdef CONFIG_PREEMPT_RCU */



#ifdef CONFIG_DEBUG_LOCK_ALLOC

static struct lock_class_key rcu_lock_key;

struct lockdep_map rcu_lock_map =