diff options
Diffstat (limited to 'drivers/gpu/nvgpu/os/posix/rwsem.c')
-rw-r--r-- | drivers/gpu/nvgpu/os/posix/rwsem.c | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/drivers/gpu/nvgpu/os/posix/rwsem.c b/drivers/gpu/nvgpu/os/posix/rwsem.c new file mode 100644 index 00000000..7a696b75 --- /dev/null +++ b/drivers/gpu/nvgpu/os/posix/rwsem.c | |||
@@ -0,0 +1,117 @@ | |||
1 | /* | ||
2 | * Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved. | ||
3 | * | ||
4 | * Permission is hereby granted, free of charge, to any person obtaining a | ||
5 | * copy of this software and associated documentation files (the "Software"), | ||
6 | * to deal in the Software without restriction, including without limitation | ||
7 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, | ||
8 | * and/or sell copies of the Software, and to permit persons to whom the | ||
9 | * Software is furnished to do so, subject to the following conditions: | ||
10 | * | ||
11 | * The above copyright notice and this permission notice shall be included in | ||
12 | * all copies or substantial portions of the Software. | ||
13 | * | ||
14 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
15 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
16 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | ||
17 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
18 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | ||
19 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | ||
20 | * DEALINGS IN THE SOFTWARE. | ||
21 | */ | ||
22 | |||
23 | #include <nvgpu/bug.h> | ||
24 | #include <nvgpu/rwsem.h> | ||
25 | #include <nvgpu/timers.h> | ||
26 | |||
27 | #include <nvgpu/posix/rwsem.h> | ||
28 | |||
29 | void nvgpu_rwsem_init(struct nvgpu_rwsem *rwsem) | ||
30 | { | ||
31 | memset(rwsem, 0, sizeof(*rwsem)); | ||
32 | |||
33 | nvgpu_spinlock_init(&rwsem->lock); | ||
34 | } | ||
35 | |||
36 | /* | ||
37 | * Acquire. | ||
38 | */ | ||
39 | void nvgpu_rwsem_down_read(struct nvgpu_rwsem *rwsem) | ||
40 | { | ||
41 | while (true) { | ||
42 | nvgpu_spinlock_acquire(&rwsem->lock); | ||
43 | |||
44 | /* | ||
45 | * If there's a writer try again. | ||
46 | */ | ||
47 | if (rwsem->writers < 0) { | ||
48 | nvgpu_spinlock_release(&rwsem->lock); | ||
49 | nvgpu_msleep(10); | ||
50 | continue; | ||
51 | } | ||
52 | |||
53 | /* | ||
54 | * Otherwise decrement the read counter and return. | ||
55 | */ | ||
56 | rwsem->readers -= 1; | ||
57 | nvgpu_spinlock_release(&rwsem->lock); | ||
58 | return; | ||
59 | } | ||
60 | } | ||
61 | |||
62 | /* | ||
63 | * Release. | ||
64 | */ | ||
65 | void nvgpu_rwsem_up_read(struct nvgpu_rwsem *rwsem) | ||
66 | { | ||
67 | nvgpu_spinlock_acquire(&rwsem->lock); | ||
68 | rwsem->readers += 1; | ||
69 | |||
70 | /* | ||
71 | * Can't be any writers if there was a reader. Also can't be | ||
72 | * a positive number of readers. The increments are always | ||
73 | * downward so if we have a positive number then there is a | ||
74 | * balancing bug. | ||
75 | */ | ||
76 | BUG_ON(rwsem->writers < 0); | ||
77 | BUG_ON(rwsem->readers > 0); | ||
78 | |||
79 | nvgpu_spinlock_release(&rwsem->lock); | ||
80 | } | ||
81 | |||
82 | void nvgpu_rwsem_down_write(struct nvgpu_rwsem *rwsem) | ||
83 | { | ||
84 | while (true) { | ||
85 | nvgpu_spinlock_acquire(&rwsem->lock); | ||
86 | |||
87 | /* | ||
88 | * If there's a reader or a writer try again. Note: in this very | ||
89 | * simple implementation it's possible for readers to | ||
90 | * indefinitely starve writers. | ||
91 | */ | ||
92 | if (rwsem->writers < 0 || rwsem->readers < 0) { | ||
93 | nvgpu_spinlock_release(&rwsem->lock); | ||
94 | nvgpu_msleep(10); | ||
95 | continue; | ||
96 | } | ||
97 | |||
98 | rwsem->writers -= 1; | ||
99 | nvgpu_spinlock_release(&rwsem->lock); | ||
100 | return; | ||
101 | } | ||
102 | } | ||
103 | |||
104 | void nvgpu_rwsem_up_write(struct nvgpu_rwsem *rwsem) | ||
105 | { | ||
106 | nvgpu_spinlock_acquire(&rwsem->lock); | ||
107 | rwsem->writers += 1; | ||
108 | |||
109 | /* | ||
110 | * Writers can't be positive: that would be an unbalanced free. Readers | ||
111 | * must be zero - otherwise this writer should never have had access! | ||
112 | */ | ||
113 | BUG_ON(rwsem->writers > 0); | ||
114 | BUG_ON(rwsem->readers != 0); | ||
115 | |||
116 | nvgpu_spinlock_release(&rwsem->lock); | ||
117 | } | ||