13  * don't try to detect the ref hitting 0 - which means that get/put can just
24  * the ref hitting 0 on every put - this would require global synchronization
28  * the ref can't hit 0 before the user drops the initial ref, so as long as we
29  * convert to non percpu mode before the initial ref is dropped everything
42 static unsigned long __percpu *percpu_count_ptr(struct percpu_ref *ref)  in percpu_count_ptr()  argument
45 		(ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC_DEAD);  in percpu_count_ptr()
50  * @ref: percpu_ref to initialize
55  * Initializes @ref.  @ref starts out in percpu mode with a refcount of 1 unless
63 int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,  in percpu_ref_init()  argument
71 	ref->percpu_count_ptr = (unsigned long)  in percpu_ref_init()
73 	if (!ref->percpu_count_ptr)  in percpu_ref_init()
76 	data = kzalloc(sizeof(*ref->data), gfp);  in percpu_ref_init()
78 		free_percpu((void __percpu *)ref->percpu_count_ptr);  in percpu_ref_init()
79 		ref->percpu_count_ptr = 0;  in percpu_ref_init()
87 		ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;  in percpu_ref_init()
94 		ref->percpu_count_ptr |= __PERCPU_REF_DEAD;  in percpu_ref_init()
102 	data->ref = ref;  in percpu_ref_init()
103 	ref->data = data;  in percpu_ref_init()
108 static void __percpu_ref_exit(struct percpu_ref *ref)  in __percpu_ref_exit()  argument
110 	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);  in __percpu_ref_exit()
114 		WARN_ON_ONCE(ref->data && ref->data->confirm_switch);  in __percpu_ref_exit()
116 		ref->percpu_count_ptr = __PERCPU_REF_ATOMIC_DEAD;  in __percpu_ref_exit()
122  * @ref: percpu_ref to exit
124  * This function exits @ref.  The caller is responsible for ensuring that
125  * @ref is no longer in active use.  The usual places to invoke this
126  * function from are the @ref->release() callback or in init failure path
130 void percpu_ref_exit(struct percpu_ref *ref)  in percpu_ref_exit()  argument
132 	struct percpu_ref_data *data = ref->data;  in percpu_ref_exit()
135 	__percpu_ref_exit(ref);  in percpu_ref_exit()
141 	ref->percpu_count_ptr |= atomic_long_read(&ref->data->count) <<  in percpu_ref_exit()
143 	ref->data = NULL;  in percpu_ref_exit()
154 	struct percpu_ref *ref = data->ref;  in percpu_ref_call_confirm_rcu()  local
156 	data->confirm_switch(ref);  in percpu_ref_call_confirm_rcu()
161 		__percpu_ref_exit(ref);  in percpu_ref_call_confirm_rcu()
163 	/* drop ref from percpu_ref_switch_to_atomic() */  in percpu_ref_call_confirm_rcu()
164 	percpu_ref_put(ref);  in percpu_ref_call_confirm_rcu()
171 	struct percpu_ref *ref = data->ref;  in percpu_ref_switch_to_atomic_rcu()  local
172 	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);  in percpu_ref_switch_to_atomic_rcu()
185 	 * to &ref->count; since gets could be happening on one cpu while puts  in percpu_ref_switch_to_atomic_rcu()
187 	 * @ref->count to hit 0 before we've got a consistent value - but the  in percpu_ref_switch_to_atomic_rcu()
191 	 * &ref->count; we need the bias value to prevent &ref->count from  in percpu_ref_switch_to_atomic_rcu()
198 		      "percpu ref (%ps) <= 0 (%ld) after switching to atomic",  in percpu_ref_switch_to_atomic_rcu()
205 	/* @ref is viewed as dead on all CPUs, send out switch confirmation */  in percpu_ref_switch_to_atomic_rcu()
209 static void percpu_ref_noop_confirm_switch(struct percpu_ref *ref)  in percpu_ref_noop_confirm_switch()  argument
213 static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref,  in __percpu_ref_switch_to_atomic()  argument
216 	if (ref->percpu_count_ptr & __PERCPU_REF_ATOMIC) {  in __percpu_ref_switch_to_atomic()
218 			confirm_switch(ref);  in __percpu_ref_switch_to_atomic()
223 	ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;  in __percpu_ref_switch_to_atomic()
229 	ref->data->confirm_switch = confirm_switch ?:  in __percpu_ref_switch_to_atomic()
232 	percpu_ref_get(ref);	/* put after confirmation */  in __percpu_ref_switch_to_atomic()
233 	call_rcu(&ref->data->rcu, percpu_ref_switch_to_atomic_rcu);  in __percpu_ref_switch_to_atomic()
236 static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)  in __percpu_ref_switch_to_percpu()  argument
238 	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);  in __percpu_ref_switch_to_percpu()
243 	if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC))  in __percpu_ref_switch_to_percpu()
246 	if (WARN_ON_ONCE(!ref->data->allow_reinit))  in __percpu_ref_switch_to_percpu()
249 	atomic_long_add(PERCPU_COUNT_BIAS, &ref->data->count);  in __percpu_ref_switch_to_percpu()
260 	smp_store_release(&ref->percpu_count_ptr,  in __percpu_ref_switch_to_percpu()
261 			  ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);  in __percpu_ref_switch_to_percpu()
264 static void __percpu_ref_switch_mode(struct percpu_ref *ref,  in __percpu_ref_switch_mode()  argument
267 	struct percpu_ref_data *data = ref->data;  in __percpu_ref_switch_mode()
279 	if (data->force_atomic || percpu_ref_is_dying(ref))  in __percpu_ref_switch_mode()
280 		__percpu_ref_switch_to_atomic(ref, confirm_switch);  in __percpu_ref_switch_mode()
282 		__percpu_ref_switch_to_percpu(ref);  in __percpu_ref_switch_mode()
287  * @ref: percpu_ref to switch to atomic mode
293  * Schedule switching of @ref to atomic mode.  All its percpu counts will
298  * operations.  Note that @ref will stay in atomic mode across kill/reinit
301  * This function may block if @ref is in the process of switching to atomic
302  * mode.  If the caller ensures that @ref is not in the process of
305 void percpu_ref_switch_to_atomic(struct percpu_ref *ref,  in percpu_ref_switch_to_atomic()  argument
312 	ref->data->force_atomic = true;  in percpu_ref_switch_to_atomic()
313 	__percpu_ref_switch_mode(ref, confirm_switch);  in percpu_ref_switch_to_atomic()
321  * @ref: percpu_ref to switch to atomic mode
323  * Schedule switching the ref to atomic mode, and wait for the
327 void percpu_ref_switch_to_atomic_sync(struct percpu_ref *ref)  in percpu_ref_switch_to_atomic_sync()  argument
329 	percpu_ref_switch_to_atomic(ref, NULL);  in percpu_ref_switch_to_atomic_sync()
330 	wait_event(percpu_ref_switch_waitq, !ref->data->confirm_switch);  in percpu_ref_switch_to_atomic_sync()
336  * @ref: percpu_ref to switch to percpu mode
339  * To re-use an expired ref, use percpu_ref_reinit().
341  * Switch @ref to percpu mode.  This function may be invoked concurrently
344  * by PERCPU_REF_INIT_ATOMIC or percpu_ref_switch_to_atomic().  If @ref is
348  * This function may block if @ref is in the process of switching to atomic
349  * mode.  If the caller ensures that @ref is not in the process of
352 void percpu_ref_switch_to_percpu(struct percpu_ref *ref)  in percpu_ref_switch_to_percpu()  argument
358 	ref->data->force_atomic = false;  in percpu_ref_switch_to_percpu()
359 	__percpu_ref_switch_mode(ref, NULL);  in percpu_ref_switch_to_percpu()
366  * percpu_ref_kill_and_confirm - drop the initial ref and schedule confirmation
367  * @ref: percpu_ref to kill
372  * called after @ref is seen as dead from all CPUs at which point all
377  * but it may block if @confirm_kill is specified and @ref is in the
382 void percpu_ref_kill_and_confirm(struct percpu_ref *ref,  in percpu_ref_kill_and_confirm()  argument
389 	WARN_ONCE(percpu_ref_is_dying(ref),  in percpu_ref_kill_and_confirm()
391 		  ref->data->release);  in percpu_ref_kill_and_confirm()
393 	ref->percpu_count_ptr |= __PERCPU_REF_DEAD;  in percpu_ref_kill_and_confirm()
394 	__percpu_ref_switch_mode(ref, confirm_kill);  in percpu_ref_kill_and_confirm()
395 	percpu_ref_put(ref);  in percpu_ref_kill_and_confirm()
403  * @ref: percpu_ref to test
405  * Returns %true if @ref reached zero.
407  * This function is safe to call as long as @ref is between init and exit.
409 bool percpu_ref_is_zero(struct percpu_ref *ref)  in percpu_ref_is_zero()  argument
414 	if (__ref_is_percpu(ref, &percpu_count))  in percpu_ref_is_zero()
419 	if (ref->data)  in percpu_ref_is_zero()
420 		count = atomic_long_read(&ref->data->count);  in percpu_ref_is_zero()
422 		count = ref->percpu_count_ptr >> __PERCPU_REF_FLAG_BITS;  in percpu_ref_is_zero()
431  * @ref: perpcu_ref to re-initialize
433  * Re-initialize @ref so that it's in the same state as when it finished
434  * percpu_ref_init() ignoring %PERCPU_REF_INIT_DEAD.  @ref must have been
437  * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
440 void percpu_ref_reinit(struct percpu_ref *ref)  in percpu_ref_reinit()  argument
442 	WARN_ON_ONCE(!percpu_ref_is_zero(ref));  in percpu_ref_reinit()
444 	percpu_ref_resurrect(ref);  in percpu_ref_reinit()
450  * @ref: perpcu_ref to resurrect
452  * Modify @ref so that it's in the same state as before percpu_ref_kill() was
453  * called. @ref must be dead but must not yet have exited.
455  * If @ref->release() frees @ref then the caller is responsible for
456  * guaranteeing that @ref->release() does not get called while this
459  * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
462 void percpu_ref_resurrect(struct percpu_ref *ref)  in percpu_ref_resurrect()  argument
469 	WARN_ON_ONCE(!percpu_ref_is_dying(ref));  in percpu_ref_resurrect()
470 	WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count));  in percpu_ref_resurrect()
472 	ref->percpu_count_ptr &= ~__PERCPU_REF_DEAD;  in percpu_ref_resurrect()
473 	percpu_ref_get(ref);  in percpu_ref_resurrect()
474 	__percpu_ref_switch_mode(ref, NULL);  in percpu_ref_resurrect()