[linux-2.6-block.git] / net / unix / garbage.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * NET3:	Garbage Collector For AF_UNIX sockets
 *
 * Garbage Collector:
 *	Copyright (C) Barak A. Pearlmutter.
 *
 * Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem.
 * If it doesn't work blame me, it worked when Barak sent it.
 *
 * Assumptions:
 *
 *  - object w/ a bit
 *  - free list
 *
 * Current optimizations:
 *
 *  - explicit stack instead of recursion
 *  - tail recurse on first born instead of immediate push/pop
 *  - we gather the stuff that should not be killed into tree
 *    and stack is just a path from root to the current pointer.
 *
 *  Future optimizations:
 *
 *  - don't just push entire root set; process in place
 *
 *  Fixes:
 *	Alan Cox	07 Sept	1997	Vmalloc internal stack as needed.
 *					Cope with changing max_files.
 *	Al Viro		11 Oct 1998
 *		Graph may have cycles. That is, we can send the descriptor
 *		of foo to bar and vice versa. Current code chokes on that.
 *		Fix: move SCM_RIGHTS ones into the separate list and then
 *		skb_free() them all instead of doing explicit fput's.
 *		Another problem: since fput() may block somebody may
 *		create a new unix_socket when we are in the middle of sweep
 *		phase. Fix: revert the logic wrt MARKED. Mark everything
 *		upon the beginning and unmark non-junk ones.
 *
 *		[12 Oct 1998] AAARGH! New code purges all SCM_RIGHTS
 *		sent to connect()'ed but still not accept()'ed sockets.
 *		Fixed. Old code had slightly different problem here:
 *		extra fput() in situation when we passed the descriptor via
 *		such socket and closed it (descriptor). That would happen on
 *		each unix_gc() until the accept(). Since the struct file in
 *		question would go to the free list and might be reused...
 *		That might be the reason of random oopses on filp_close()
 *		in unrelated processes.
 *
 *	AV		28 Feb 1999
 *		Kill the explicit allocation of stack. Now we keep the tree
 *		with root in dummy + pointer (gc_current) to one of the nodes.
 *		Stack is represented as path from gc_current to dummy. Unmark
 *		now means "add to tree". Push == "make it a son of gc_current".
 *		Pop == "move gc_current to parent". We keep only pointers to
 *		parents (->gc_tree).
 *	AV		1 Mar 1999
 *		Damn. Added missing check for ->dead in listen queues scanning.
 *
 *	Miklos Szeredi 25 Jun 2007
 *		Reimplement with a cycle collecting algorithm. This should
 *		solve several problems with the previous code, like being racy
 *		wrt receive and holding up unrelated socket operations.
 */

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/net.h>
#include <linux/fs.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <linux/wait.h>

#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <net/tcp_states.h>

#include "scm.h"

/* Internal data structures and random procedures: */

static LIST_HEAD(gc_candidates);
static DECLARE_WAIT_QUEUE_HEAD(unix_gc_wait);

static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
			  struct sk_buff_head *hitlist)
{
	struct sk_buff *skb;
	struct sk_buff *next;

	spin_lock(&x->sk_receive_queue.lock);
	skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
		/* Do we have file descriptors ? */
		if (UNIXCB(skb).fp) {
			bool hit = false;
			/* Process the descriptors of this socket */
			int nfd = UNIXCB(skb).fp->count;
			struct file **fp = UNIXCB(skb).fp->fp;

			while (nfd--) {
				/* Get the socket the fd matches if it indeed does so */
				struct sock *sk = unix_get_socket(*fp++);

				if (sk) {
					struct unix_sock *u = unix_sk(sk);

					/* Ignore non-candidates, they could
					 * have been added to the queues after
					 * starting the garbage collection
					 */
					if (test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
						hit = true;

						func(u);
					}
				}
			}
			if (hit && hitlist != NULL) {
				__skb_unlink(skb, &x->sk_receive_queue);
				__skb_queue_tail(hitlist, skb);
			}
		}
	}
	spin_unlock(&x->sk_receive_queue.lock);
}

static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
			  struct sk_buff_head *hitlist)
{
	if (x->sk_state != TCP_LISTEN) {
		scan_inflight(x, func, hitlist);
	} else {
		struct sk_buff *skb;
		struct sk_buff *next;
		struct unix_sock *u;
		LIST_HEAD(embryos);

		/* For a listening socket collect the queued embryos
		 * and perform a scan on them as well.
		 */
		spin_lock(&x->sk_receive_queue.lock);
		skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
			u = unix_sk(skb->sk);

			/* An embryo cannot be in-flight, so it's safe
			 * to use the list link.
			 */
			BUG_ON(!list_empty(&u->link));
			list_add_tail(&u->link, &embryos);
		}
		spin_unlock(&x->sk_receive_queue.lock);

		while (!list_empty(&embryos)) {
			u = list_entry(embryos.next, struct unix_sock, link);
			scan_inflight(&u->sk, func, hitlist);
			list_del_init(&u->link);
		}
	}
}

static void dec_inflight(struct unix_sock *usk)
{
	atomic_long_dec(&usk->inflight);
}

static void inc_inflight(struct unix_sock *usk)
{
	atomic_long_inc(&usk->inflight);
}

static void inc_inflight_move_tail(struct unix_sock *u)
{
	atomic_long_inc(&u->inflight);
	/* If this still might be part of a cycle, move it to the end
	 * of the list, so that it's checked even if it was already
	 * passed over
	 */
	if (test_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags))
		list_move_tail(&u->link, &gc_candidates);
}

static bool gc_in_progress;
#define UNIX_INFLIGHT_TRIGGER_GC 16000

void wait_for_unix_gc(void)
{
	/* If number of inflight sockets is insane,
	 * force a garbage collect right now.
	 */
	if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
		unix_gc();
	wait_event(unix_gc_wait, gc_in_progress == false);
}

/* The external entry point: unix_gc() */
void unix_gc(void)
{
	struct unix_sock *u;
	struct unix_sock *next;
	struct sk_buff_head hitlist;
	struct list_head cursor;
	LIST_HEAD(not_cycle_list);

	spin_lock(&unix_gc_lock);

	/* Avoid a recursive GC. */
	if (gc_in_progress)
		goto out;

	gc_in_progress = true;
	/* First, select candidates for garbage collection.  Only
	 * in-flight sockets are considered, and from those only ones
	 * which don't have any external reference.
	 *
	 * Holding unix_gc_lock will protect these candidates from
	 * being detached, and hence from gaining an external
	 * reference.  Since there are no possible receivers, all
	 * buffers currently on the candidates' queues stay there
	 * during the garbage collection.
	 *
	 * We also know that no new candidate can be added onto the
	 * receive queues.  Other, non candidate sockets _can_ be
	 * added to queue, so we must make sure only to touch
	 * candidates.
	 */
	list_for_each_entry_safe(u, next, &gc_inflight_list, link) {
		long total_refs;
		long inflight_refs;

		total_refs = file_count(u->sk.sk_socket->file);
		inflight_refs = atomic_long_read(&u->inflight);

		BUG_ON(inflight_refs < 1);
		BUG_ON(total_refs < inflight_refs);
		if (total_refs == inflight_refs) {
			list_move_tail(&u->link, &gc_candidates);
			__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
			__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
		}
	}

	/* Now remove all internal in-flight reference to children of
	 * the candidates.
	 */
	list_for_each_entry(u, &gc_candidates, link)
		scan_children(&u->sk, dec_inflight, NULL);

	/* Restore the references for children of all candidates,
	 * which have remaining references.  Do this recursively, so
	 * only those remain, which form cyclic references.
	 *
	 * Use a "cursor" link, to make the list traversal safe, even
	 * though elements might be moved about.
	 */
	list_add(&cursor, &gc_candidates);
	while (cursor.next != &gc_candidates) {
		u = list_entry(cursor.next, struct unix_sock, link);

		/* Move cursor to after the current position. */
		list_move(&cursor, &u->link);

		if (atomic_long_read(&u->inflight) > 0) {
			list_move_tail(&u->link, &not_cycle_list);
			__clear_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
			scan_children(&u->sk, inc_inflight_move_tail, NULL);
		}
	}
	list_del(&cursor);

	/* Now gc_candidates contains only garbage.  Restore original
	 * inflight counters for these as well, and remove the skbuffs
	 * which are creating the cycle(s).
	 */
	skb_queue_head_init(&hitlist);
	list_for_each_entry(u, &gc_candidates, link)
		scan_children(&u->sk, inc_inflight, &hitlist);

	/* not_cycle_list contains those sockets which do not make up a
	 * cycle.  Restore these to the inflight list.
	 */
	while (!list_empty(&not_cycle_list)) {
		u = list_entry(not_cycle_list.next, struct unix_sock, link);
		__clear_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
		list_move_tail(&u->link, &gc_inflight_list);
	}

	spin_unlock(&unix_gc_lock);

	/* Here we are. Hitlist is filled. Die. */
	__skb_queue_purge(&hitlist);

	spin_lock(&unix_gc_lock);

	/* All candidates should have been detached by now. */
	BUG_ON(!list_empty(&gc_candidates));
	gc_in_progress = false;
	wake_up(&unix_gc_wait);

 out:
	spin_unlock(&unix_gc_lock);
}
Commit	Line	Data
a85036f6	1	// SPDX-License-Identifier: GPL-2.0-or-later
1da177e4 LT	2	/*
	3	* NET3: Garbage Collector For AF_UNIX sockets
	4	*
	5	* Garbage Collector:
	6	* Copyright (C) Barak A. Pearlmutter.
1da177e4 LT	7	*
	8	* Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem.
	9	* If it doesn't work blame me, it worked when Barak sent it.
	10	*
	11	* Assumptions:
	12	*
	13	* - object w/ a bit
	14	* - free list
	15	*
	16	* Current optimizations:
	17	*
	18	* - explicit stack instead of recursion
	19	* - tail recurse on first born instead of immediate push/pop
	20	* - we gather the stuff that should not be killed into tree
	21	* and stack is just a path from root to the current pointer.
	22	*
	23	* Future optimizations:
	24	*
	25	* - don't just push entire root set; process in place
	26	*
1da177e4 LT	27	* Fixes:
	28	* Alan Cox 07 Sept 1997 Vmalloc internal stack as needed.
	29	* Cope with changing max_files.
	30	* Al Viro 11 Oct 1998
	31	* Graph may have cycles. That is, we can send the descriptor
	32	* of foo to bar and vice versa. Current code chokes on that.
	33	* Fix: move SCM_RIGHTS ones into the separate list and then
	34	* skb_free() them all instead of doing explicit fput's.
	35	* Another problem: since fput() may block somebody may
	36	* create a new unix_socket when we are in the middle of sweep
	37	* phase. Fix: revert the logic wrt MARKED. Mark everything
	38	* upon the beginning and unmark non-junk ones.
	39	*
	40	* [12 Oct 1998] AAARGH! New code purges all SCM_RIGHTS
	41	* sent to connect()'ed but still not accept()'ed sockets.
	42	* Fixed. Old code had slightly different problem here:
	43	* extra fput() in situation when we passed the descriptor via
	44	* such socket and closed it (descriptor). That would happen on
	45	* each unix_gc() until the accept(). Since the struct file in
	46	* question would go to the free list and might be reused...
	47	* That might be the reason of random oopses on filp_close()
	48	* in unrelated processes.
	49	*
	50	* AV 28 Feb 1999
	51	* Kill the explicit allocation of stack. Now we keep the tree
	52	* with root in dummy + pointer (gc_current) to one of the nodes.
	53	* Stack is represented as path from gc_current to dummy. Unmark
	54	* now means "add to tree". Push == "make it a son of gc_current".
	55	* Pop == "move gc_current to parent". We keep only pointers to
	56	* parents (->gc_tree).
	57	* AV 1 Mar 1999
	58	* Damn. Added missing check for ->dead in listen queues scanning.
	59	*
1fd05ba5 MS	60	* Miklos Szeredi 25 Jun 2007
	61	* Reimplement with a cycle collecting algorithm. This should
	62	* solve several problems with the previous code, like being racy
	63	* wrt receive and holding up unrelated socket operations.
1da177e4	64	*/
ac7bfa62	65
1da177e4	66	#include <linux/kernel.h>
1da177e4 LT	67	#include <linux/string.h>
	68	#include <linux/socket.h>
	69	#include <linux/un.h>
	70	#include <linux/net.h>
	71	#include <linux/fs.h>
1da177e4 LT	72	#include <linux/skbuff.h>
	73	#include <linux/netdevice.h>
	74	#include <linux/file.h>
	75	#include <linux/proc_fs.h>
4a3e2f71	76	#include <linux/mutex.h>
5f23b734	77	#include <linux/wait.h>
1da177e4 LT	78
	79	#include <net/sock.h>
	80	#include <net/af_unix.h>
	81	#include <net/scm.h>
c752f073	82	#include <net/tcp_states.h>
1da177e4	83
f4e65870 JA	84	#include "scm.h"
f4e65870 JA	85
1da177e4 LT	86	/* Internal data structures and random procedures: */
1da177e4 LT	87
1fd05ba5	88	static LIST_HEAD(gc_candidates);
5f23b734	89	static DECLARE_WAIT_QUEUE_HEAD(unix_gc_wait);
1da177e4	90
5c80f1ae	91	static void scan_inflight(struct sock x, void (func)(struct unix_sock *),
1fd05ba5	92	struct sk_buff_head *hitlist)
1da177e4	93	{
1fd05ba5 MS	94	struct sk_buff *skb;
	95	struct sk_buff *next;
	96
	97	spin_lock(&x->sk_receive_queue.lock);
a2f3be17	98	skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
d1ab39f1	99	/* Do we have file descriptors ? */
1fd05ba5 MS	100	if (UNIXCB(skb).fp) {
1fd05ba5 MS	101	bool hit = false;
d1ab39f1	102	/* Process the descriptors of this socket */
1fd05ba5 MS	103	int nfd = UNIXCB(skb).fp->count;
1fd05ba5 MS	104	struct file **fp = UNIXCB(skb).fp->fp;
d1ab39f1	105
1fd05ba5	106	while (nfd--) {
d1ab39f1	107	/* Get the socket the fd matches if it indeed does so */
1fd05ba5	108	struct sock sk = unix_get_socket(fp++);
d1ab39f1	109
5c80f1ae	110	if (sk) {
6209344f MS	111	struct unix_sock *u = unix_sk(sk);
6209344f MS	112
d1ab39f1	113	/* Ignore non-candidates, they could
6209344f MS	114	* have been added to the queues after
	115	* starting the garbage collection
	116	*/
60bc851a	117	if (test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
6209344f	118	hit = true;
d1ab39f1	119
6209344f MS	120	func(u);
6209344f MS	121	}
1fd05ba5 MS	122	}
	123	}
	124	if (hit && hitlist != NULL) {
	125	__skb_unlink(skb, &x->sk_receive_queue);
	126	__skb_queue_tail(hitlist, skb);
	127	}
	128	}
	129	}
	130	spin_unlock(&x->sk_receive_queue.lock);
1da177e4 LT	131	}
1da177e4 LT	132
5c80f1ae	133	static void scan_children(struct sock x, void (func)(struct unix_sock *),
1fd05ba5	134	struct sk_buff_head *hitlist)
1da177e4	135	{
d1ab39f1	136	if (x->sk_state != TCP_LISTEN) {
1fd05ba5	137	scan_inflight(x, func, hitlist);
d1ab39f1	138	} else {
1fd05ba5 MS	139	struct sk_buff *skb;
	140	struct sk_buff *next;
	141	struct unix_sock *u;
	142	LIST_HEAD(embryos);
	143
d1ab39f1	144	/* For a listening socket collect the queued embryos
1fd05ba5 MS	145	* and perform a scan on them as well.
	146	*/
	147	spin_lock(&x->sk_receive_queue.lock);
a2f3be17	148	skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
1fd05ba5 MS	149	u = unix_sk(skb->sk);
1fd05ba5 MS	150
d1ab39f1	151	/* An embryo cannot be in-flight, so it's safe
1fd05ba5 MS	152	* to use the list link.
	153	*/
	154	BUG_ON(!list_empty(&u->link));
	155	list_add_tail(&u->link, &embryos);
	156	}
	157	spin_unlock(&x->sk_receive_queue.lock);
	158
	159	while (!list_empty(&embryos)) {
	160	u = list_entry(embryos.next, struct unix_sock, link);
	161	scan_inflight(&u->sk, func, hitlist);
	162	list_del_init(&u->link);
	163	}
	164	}
1da177e4 LT	165	}
1da177e4 LT	166
5c80f1ae	167	static void dec_inflight(struct unix_sock *usk)
1da177e4	168	{
516e0cc5	169	atomic_long_dec(&usk->inflight);
1fd05ba5	170	}
1da177e4	171
5c80f1ae	172	static void inc_inflight(struct unix_sock *usk)
1fd05ba5	173	{
516e0cc5	174	atomic_long_inc(&usk->inflight);
1da177e4 LT	175	}
1da177e4 LT	176
5c80f1ae	177	static void inc_inflight_move_tail(struct unix_sock *u)
1fd05ba5	178	{
516e0cc5	179	atomic_long_inc(&u->inflight);
d1ab39f1	180	/* If this still might be part of a cycle, move it to the end
6209344f MS	181	* of the list, so that it's checked even if it was already
6209344f MS	182	* passed over
1fd05ba5	183	*/
60bc851a	184	if (test_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags))
1fd05ba5 MS	185	list_move_tail(&u->link, &gc_candidates);
1fd05ba5 MS	186	}
1da177e4	187
505e907d	188	static bool gc_in_progress;
9915672d	189	#define UNIX_INFLIGHT_TRIGGER_GC 16000
1da177e4	190
5f23b734	191	void wait_for_unix_gc(void)
1da177e4	192	{
d1ab39f1	193	/* If number of inflight sockets is insane,
9915672d ED	194	* force a garbage collect right now.
	195	*/
	196	if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
	197	unix_gc();
5f23b734	198	wait_event(unix_gc_wait, gc_in_progress == false);
5f23b734	199	}
1da177e4	200
5f23b734	201	/* The external entry point: unix_gc() */
	202	void unix_gc(void)
	203	{
1fd05ba5 MS	204	struct unix_sock *u;
	205	struct unix_sock *next;
	206	struct sk_buff_head hitlist;
	207	struct list_head cursor;
6209344f	208	LIST_HEAD(not_cycle_list);
1da177e4	209
1fd05ba5	210	spin_lock(&unix_gc_lock);
1da177e4	211
1fd05ba5 MS	212	/* Avoid a recursive GC. */
	213	if (gc_in_progress)
	214	goto out;
1da177e4	215
1fd05ba5	216	gc_in_progress = true;
d1ab39f1	217	/* First, select candidates for garbage collection. Only
1fd05ba5 MS	218	* in-flight sockets are considered, and from those only ones
	219	* which don't have any external reference.
	220	*
	221	* Holding unix_gc_lock will protect these candidates from
	222	* being detached, and hence from gaining an external
6209344f MS	223	* reference. Since there are no possible receivers, all
	224	* buffers currently on the candidates' queues stay there
	225	* during the garbage collection.
	226	*
	227	* We also know that no new candidate can be added onto the
	228	* receive queues. Other, non candidate sockets _can_ be
	229	* added to queue, so we must make sure only to touch
	230	* candidates.
1da177e4	231	*/
1fd05ba5	232	list_for_each_entry_safe(u, next, &gc_inflight_list, link) {
516e0cc5 AV	233	long total_refs;
516e0cc5 AV	234	long inflight_refs;
1fd05ba5 MS	235
1fd05ba5 MS	236	total_refs = file_count(u->sk.sk_socket->file);
516e0cc5	237	inflight_refs = atomic_long_read(&u->inflight);
1fd05ba5 MS	238
	239	BUG_ON(inflight_refs < 1);
	240	BUG_ON(total_refs < inflight_refs);
	241	if (total_refs == inflight_refs) {
	242	list_move_tail(&u->link, &gc_candidates);
60bc851a ED	243	__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
60bc851a ED	244	__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
1fd05ba5 MS	245	}
1fd05ba5 MS	246	}
1da177e4	247
d1ab39f1	248	/* Now remove all internal in-flight reference to children of
1fd05ba5	249	* the candidates.
1da177e4	250	*/
1fd05ba5 MS	251	list_for_each_entry(u, &gc_candidates, link)
1fd05ba5 MS	252	scan_children(&u->sk, dec_inflight, NULL);
1da177e4	253
d1ab39f1	254	/* Restore the references for children of all candidates,
1fd05ba5 MS	255	* which have remaining references. Do this recursively, so
	256	* only those remain, which form cyclic references.
	257	*
	258	* Use a "cursor" link, to make the list traversal safe, even
	259	* though elements might be moved about.
1da177e4	260	*/
1fd05ba5 MS	261	list_add(&cursor, &gc_candidates);
	262	while (cursor.next != &gc_candidates) {
	263	u = list_entry(cursor.next, struct unix_sock, link);
1da177e4	264
1fd05ba5 MS	265	/* Move cursor to after the current position. */
1fd05ba5 MS	266	list_move(&cursor, &u->link);
ac7bfa62	267
516e0cc5	268	if (atomic_long_read(&u->inflight) > 0) {
6209344f	269	list_move_tail(&u->link, &not_cycle_list);
60bc851a	270	__clear_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
1fd05ba5	271	scan_children(&u->sk, inc_inflight_move_tail, NULL);
1da177e4	272	}
1da177e4	273	}
1fd05ba5	274	list_del(&cursor);
1da177e4	275
7df9c246 AU	276	/* Now gc_candidates contains only garbage. Restore original
	277	* inflight counters for these as well, and remove the skbuffs
	278	* which are creating the cycle(s).
	279	*/
	280	skb_queue_head_init(&hitlist);
	281	list_for_each_entry(u, &gc_candidates, link)
	282	scan_children(&u->sk, inc_inflight, &hitlist);
	283
d1ab39f1	284	/* not_cycle_list contains those sockets which do not make up a
6209344f MS	285	* cycle. Restore these to the inflight list.
	286	*/
	287	while (!list_empty(&not_cycle_list)) {
	288	u = list_entry(not_cycle_list.next, struct unix_sock, link);
60bc851a	289	__clear_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
6209344f MS	290	list_move_tail(&u->link, &gc_inflight_list);
	291	}
	292
1fd05ba5	293	spin_unlock(&unix_gc_lock);
1da177e4	294
1fd05ba5 MS	295	/* Here we are. Hitlist is filled. Die. */
1fd05ba5 MS	296	__skb_queue_purge(&hitlist);
1da177e4	297
1fd05ba5	298	spin_lock(&unix_gc_lock);
1da177e4	299
1fd05ba5 MS	300	/* All candidates should have been detached by now. */
	301	BUG_ON(!list_empty(&gc_candidates));
	302	gc_in_progress = false;
5f23b734	303	wake_up(&unix_gc_wait);
1da177e4	304
1fd05ba5 MS	305	out:
1fd05ba5 MS	306	spin_unlock(&unix_gc_lock);
1da177e4	307	}