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Commit 9e804d1f authored by Tejun Heo's avatar Tejun Heo
Browse files

percpu_ref: rename things to prepare for decoupling percpu/atomic mode switch 



percpu_ref will be restructured so that percpu/atomic mode switching
and reference killing are dedoupled.  In preparation, do the following
renames.

* percpu_ref->confirm_kill	-> percpu_ref->confirm_switch
* __PERCPU_REF_DEAD		-> __PERCPU_REF_ATOMIC
* __percpu_ref_alive()		-> __ref_is_percpu()

This patch is pure rename and doesn't introduce any functional
changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarKent Overstreet <kmo@daterainc.com>
parent eecc16ba

include/linux/percpu-refcount.h

+14 −11
Original line number Diff line number Diff line
@@ -54,6 +54,11 @@ 
struct percpu_ref;

typedef void (percpu_ref_func_t)(struct percpu_ref *);



/* flags set in the lower bits of percpu_ref->percpu_count_ptr */

enum {

	__PERCPU_REF_ATOMIC	= 1LU << 0,	/* operating in atomic mode */

};



struct percpu_ref {

	atomic_long_t		count;

	/*
@@ -62,7 +67,7 @@ struct percpu_ref { 
	 */

	unsigned long		percpu_count_ptr;

	percpu_ref_func_t	*release;

	percpu_ref_func_t	*confirm_kill;

	percpu_ref_func_t	*confirm_switch;

	struct rcu_head		rcu;

};
@@ -88,15 +93,13 @@ static inline void percpu_ref_kill(struct percpu_ref *ref) 
	return percpu_ref_kill_and_confirm(ref, NULL);

}



#define __PERCPU_REF_DEAD	1



/*

 * Internal helper.  Don't use outside percpu-refcount proper.  The

 * function doesn't return the pointer and let the caller test it for NULL

 * because doing so forces the compiler to generate two conditional

 * branches as it can't assume that @ref->percpu_count is not NULL.

 */

static inline bool __percpu_ref_alive(struct percpu_ref *ref,

static inline bool __ref_is_percpu(struct percpu_ref *ref,

					  unsigned long __percpu **percpu_countp)

{

	unsigned long percpu_ptr = ACCESS_ONCE(ref->percpu_count_ptr);
@@ -104,7 +107,7 @@ static inline bool __percpu_ref_alive(struct percpu_ref *ref, 
	/* paired with smp_store_release() in percpu_ref_reinit() */

	smp_read_barrier_depends();



	if (unlikely(percpu_ptr & __PERCPU_REF_DEAD))

	if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))

		return false;



	*percpu_countp = (unsigned long __percpu *)percpu_ptr;
@@ -125,7 +128,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref) 


	rcu_read_lock_sched();



	if (__percpu_ref_alive(ref, &percpu_count))

	if (__ref_is_percpu(ref, &percpu_count))

		this_cpu_inc(*percpu_count);

	else

		atomic_long_inc(&ref->count);
@@ -149,7 +152,7 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) 


	rcu_read_lock_sched();



	if (__percpu_ref_alive(ref, &percpu_count)) {

	if (__ref_is_percpu(ref, &percpu_count)) {

		this_cpu_inc(*percpu_count);

		ret = true;

	} else {
@@ -183,7 +186,7 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) 


	rcu_read_lock_sched();



	if (__percpu_ref_alive(ref, &percpu_count)) {

	if (__ref_is_percpu(ref, &percpu_count)) {

		this_cpu_inc(*percpu_count);

		ret = true;

	}
@@ -208,7 +211,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref) 


	rcu_read_lock_sched();



	if (__percpu_ref_alive(ref, &percpu_count))

	if (__ref_is_percpu(ref, &percpu_count))

		this_cpu_dec(*percpu_count);

	else if (unlikely(atomic_long_dec_and_test(&ref->count)))

		ref->release(ref);
@@ -228,7 +231,7 @@ static inline bool percpu_ref_is_zero(struct percpu_ref *ref) 
{

	unsigned long __percpu *percpu_count;



	if (__percpu_ref_alive(ref, &percpu_count))

	if (__ref_is_percpu(ref, &percpu_count))

		return false;

	return !atomic_long_read(&ref->count);

}

lib/percpu-refcount.c

+11 −11
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ 
static unsigned long __percpu *percpu_count_ptr(struct percpu_ref *ref)

{

	return (unsigned long __percpu *)

		(ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);

		(ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);

}



/**
@@ -80,7 +80,7 @@ void percpu_ref_exit(struct percpu_ref *ref) 


	if (percpu_count) {

		free_percpu(percpu_count);

		ref->percpu_count_ptr = __PERCPU_REF_DEAD;

		ref->percpu_count_ptr = __PERCPU_REF_ATOMIC;

	}

}

EXPORT_SYMBOL_GPL(percpu_ref_exit);
@@ -117,8 +117,8 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
		  ref->release, atomic_long_read(&ref->count));



	/* @ref is viewed as dead on all CPUs, send out kill confirmation */

	if (ref->confirm_kill)

		ref->confirm_kill(ref);

	if (ref->confirm_switch)

		ref->confirm_switch(ref);



	/*

	 * Now we're in single atomic_long_t mode with a consistent
@@ -145,11 +145,11 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
void percpu_ref_kill_and_confirm(struct percpu_ref *ref,

				 percpu_ref_func_t *confirm_kill)

{

	WARN_ONCE(ref->percpu_count_ptr & __PERCPU_REF_DEAD,

	WARN_ONCE(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC,

		  "%s called more than once on %pf!", __func__, ref->release);



	ref->percpu_count_ptr |= __PERCPU_REF_DEAD;

	ref->confirm_kill = confirm_kill;

	ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;

	ref->confirm_switch = confirm_kill;



	call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);

}
@@ -178,14 +178,14 @@ void percpu_ref_reinit(struct percpu_ref *ref) 


	/*

	 * Restore per-cpu operation.  smp_store_release() is paired with

	 * smp_read_barrier_depends() in __percpu_ref_alive() and

	 * guarantees that the zeroing is visible to all percpu accesses

	 * which can see the following __PERCPU_REF_DEAD clearing.

	 * smp_read_barrier_depends() in __ref_is_percpu() and guarantees

	 * that the zeroing is visible to all percpu accesses which can see

	 * the following __PERCPU_REF_ATOMIC clearing.

	 */

	for_each_possible_cpu(cpu)

		*per_cpu_ptr(percpu_count, cpu) = 0;



	smp_store_release(&ref->percpu_count_ptr,

			  ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);

			  ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);

}

EXPORT_SYMBOL_GPL(percpu_ref_reinit);