Eric Lee / smarc-fsl-linux-kernel

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Commit ecf7ace9a8450303a987aa8364e53860cd50e554

Authored by Thomas Hellstrom
Committed by Dave Airlie
1 parent d6ea88865d

kref: Add a kref_sub function 

Makes it possible to optimize batched multiple unrefs.
Initial user will be drivers/gpu/ttm which accumulates unrefs to be
processed outside of atomic code.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Showing 2 changed files with 32 additions and 0 deletions Inline Diff

include/linux/kref.h
Diff comments   View file @ ecf7ace
1 /* 1 /*
2 * kref.h - library routines for handling generic reference counted objects 2 * kref.h - library routines for handling generic reference counted objects
3 * 3 *
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> 4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Corp. 5 * Copyright (C) 2004 IBM Corp.
6 * 6 *
7 * based on kobject.h which was: 7 * based on kobject.h which was:
8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> 8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
9 * Copyright (C) 2002-2003 Open Source Development Labs 9 * Copyright (C) 2002-2003 Open Source Development Labs
10 * 10 *
11 * This file is released under the GPLv2. 11 * This file is released under the GPLv2.
12 * 12 *
13 */ 13 */
14 14
15 #ifndef _KREF_H_ 15 #ifndef _KREF_H_
16 #define _KREF_H_ 16 #define _KREF_H_
17 17
18 #include <linux/types.h> 18 #include <linux/types.h>
19 19
20 struct kref { 20 struct kref {
21 atomic_t refcount; 21 atomic_t refcount;
22 }; 22 };
23 23
24 void kref_init(struct kref *kref); 24 void kref_init(struct kref *kref);
25 void kref_get(struct kref *kref); 25 void kref_get(struct kref *kref);
26 int kref_put(struct kref *kref, void (*release) (struct kref *kref)); 26 int kref_put(struct kref *kref, void (*release) (struct kref *kref));
27 int kref_sub(struct kref *kref, unsigned int count,
28 void (*release) (struct kref *kref));
27 29
28 #endif /* _KREF_H_ */ 30 #endif /* _KREF_H_ */
29 31
1 /* 1 /*
2 * kref.c - library routines for handling generic reference counted objects 2 * kref.c - library routines for handling generic reference counted objects
3 * 3 *
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> 4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Corp. 5 * Copyright (C) 2004 IBM Corp.
6 * 6 *
7 * based on lib/kobject.c which was: 7 * based on lib/kobject.c which was:
8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> 8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
9 * 9 *
10 * This file is released under the GPLv2. 10 * This file is released under the GPLv2.
11 * 11 *
12 */ 12 */
13 13
14 #include <linux/kref.h> 14 #include <linux/kref.h>
15 #include <linux/module.h> 15 #include <linux/module.h>
16 #include <linux/slab.h> 16 #include <linux/slab.h>
17 17
18 /** 18 /**
19 * kref_init - initialize object. 19 * kref_init - initialize object.
20 * @kref: object in question. 20 * @kref: object in question.
21 */ 21 */
22 void kref_init(struct kref *kref) 22 void kref_init(struct kref *kref)
23 { 23 {
24 atomic_set(&kref->refcount, 1); 24 atomic_set(&kref->refcount, 1);
25 smp_mb(); 25 smp_mb();
26 } 26 }
27 27
28 /** 28 /**
29 * kref_get - increment refcount for object. 29 * kref_get - increment refcount for object.
30 * @kref: object. 30 * @kref: object.
31 */ 31 */
32 void kref_get(struct kref *kref) 32 void kref_get(struct kref *kref)
33 { 33 {
34 WARN_ON(!atomic_read(&kref->refcount)); 34 WARN_ON(!atomic_read(&kref->refcount));
35 atomic_inc(&kref->refcount); 35 atomic_inc(&kref->refcount);
36 smp_mb__after_atomic_inc(); 36 smp_mb__after_atomic_inc();
37 } 37 }
38 38
39 /** 39 /**
40 * kref_put - decrement refcount for object. 40 * kref_put - decrement refcount for object.
41 * @kref: object. 41 * @kref: object.
42 * @release: pointer to the function that will clean up the object when the 42 * @release: pointer to the function that will clean up the object when the
43 * last reference to the object is released. 43 * last reference to the object is released.
44 * This pointer is required, and it is not acceptable to pass kfree 44 * This pointer is required, and it is not acceptable to pass kfree
45 * in as this function. 45 * in as this function.
46 * 46 *
47 * Decrement the refcount, and if 0, call release(). 47 * Decrement the refcount, and if 0, call release().
48 * Return 1 if the object was removed, otherwise return 0. Beware, if this 48 * Return 1 if the object was removed, otherwise return 0. Beware, if this
49 * function returns 0, you still can not count on the kref from remaining in 49 * function returns 0, you still can not count on the kref from remaining in
50 * memory. Only use the return value if you want to see if the kref is now 50 * memory. Only use the return value if you want to see if the kref is now
51 * gone, not present. 51 * gone, not present.
52 */ 52 */
53 int kref_put(struct kref *kref, void (*release)(struct kref *kref)) 53 int kref_put(struct kref *kref, void (*release)(struct kref *kref))
54 { 54 {
55 WARN_ON(release == NULL); 55 WARN_ON(release == NULL);
56 WARN_ON(release == (void (*)(struct kref *))kfree); 56 WARN_ON(release == (void (*)(struct kref *))kfree);
57 57
58 if (atomic_dec_and_test(&kref->refcount)) { 58 if (atomic_dec_and_test(&kref->refcount)) {
59 release(kref); 59 release(kref);
60 return 1; 60 return 1;
61 } 61 }
62 return 0; 62 return 0;
63 } 63 }
64 64
65
66 /**
67 * kref_sub - subtract a number of refcounts for object.
68 * @kref: object.
69 * @count: Number of recounts to subtract.
70 * @release: pointer to the function that will clean up the object when the
71 * last reference to the object is released.
72 * This pointer is required, and it is not acceptable to pass kfree
73 * in as this function.
74 *
75 * Subtract @count from the refcount, and if 0, call release().
76 * Return 1 if the object was removed, otherwise return 0. Beware, if this
77 * function returns 0, you still can not count on the kref from remaining in
78 * memory. Only use the return value if you want to see if the kref is now
79 * gone, not present.
80 */
81 int kref_sub(struct kref *kref, unsigned int count,
82 void (*release)(struct kref *kref))
83 {
84 WARN_ON(release == NULL);
85 WARN_ON(release == (void (*)(struct kref *))kfree);
86
87 if (atomic_sub_and_test((int) count, &kref->refcount)) {
88 release(kref);
89 return 1;
90 }
91 return 0;
92 }
93
65 EXPORT_SYMBOL(kref_init); 94 EXPORT_SYMBOL(kref_init);
66 EXPORT_SYMBOL(kref_get); 95 EXPORT_SYMBOL(kref_get);
67 EXPORT_SYMBOL(kref_put); 96 EXPORT_SYMBOL(kref_put);
97 EXPORT_SYMBOL(kref_sub);
68 98