diff options
author | Lin Yongting <linyongting@gmail.com> | 2014-04-16 11:25:28 -0400 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-16 17:13:26 -0400 |
commit | 06d96c0ff77f20dbf5fc93c8cfa9a2a9690fd67e (patch) | |
tree | f335638935b2082dc0493bbae0aa9867d2f64fd6 /Documentation/zh_CN/io_ordering.txt | |
parent | 408065998443831d3369c6bfdc8862c1d02a91dd (diff) |
Chinese: add translation of io_ordering.txt
This is a Chinese translated version of Documentation/io_ordering.txt
Signed-off-by: Lin Yongting <linyongting@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/zh_CN/io_ordering.txt')
-rw-r--r-- | Documentation/zh_CN/io_ordering.txt | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/Documentation/zh_CN/io_ordering.txt b/Documentation/zh_CN/io_ordering.txt new file mode 100644 index 000000000000..e592daf4e014 --- /dev/null +++ b/Documentation/zh_CN/io_ordering.txt | |||
@@ -0,0 +1,67 @@ | |||
1 | Chinese translated version of Documentation/io_orderings.txt | ||
2 | |||
3 | If you have any comment or update to the content, please contact the | ||
4 | original document maintainer directly. However, if you have a problem | ||
5 | communicating in English you can also ask the Chinese maintainer for | ||
6 | help. Contact the Chinese maintainer if this translation is outdated | ||
7 | or if there is a problem with the translation. | ||
8 | |||
9 | Chinese maintainer: Lin Yongting <linyongting@gmail.com> | ||
10 | --------------------------------------------------------------------- | ||
11 | Documentation/io_ordering.txt 的中文翻译 | ||
12 | |||
13 | 如果想评论或更新本文的内容,请直接联系原文档的维护者。如果你使用英文 | ||
14 | 交流有困难的话,也可以向中文版维护者求助。如果本翻译更新不及时或者翻 | ||
15 | 译存在问题,请联系中文版维护者。 | ||
16 | |||
17 | 中文版维护者: 林永听 Lin Yongting <linyongting@gmail.com> | ||
18 | 中文版翻译者: 林永听 Lin Yongting <linyongting@gmail.com> | ||
19 | 中文版校译者: 林永听 Lin Yongting <linyongting@gmail.com> | ||
20 | |||
21 | |||
22 | 以下为正文 | ||
23 | --------------------------------------------------------------------- | ||
24 | |||
25 | 在某些平台上,所谓的内存映射I/O是弱顺序。在这些平台上,驱动开发者有责任 | ||
26 | 保证I/O内存映射地址的写操作按程序图意的顺序达到设备。通常读取一个“安全” | ||
27 | 设备寄存器或桥寄存器,触发IO芯片清刷未处理的写操作到达设备后才处理读操作, | ||
28 | 而达到保证目的。驱动程序通常在spinlock保护的临界区退出之前使用这种技术。 | ||
29 | 这也可以保证后面的写操作只在前面的写操作之后到达设备(这非常类似于内存 | ||
30 | 屏障操作,mb(),不过仅适用于I/O)。 | ||
31 | |||
32 | 假设一个设备驱动程的具体例子: | ||
33 | |||
34 | ... | ||
35 | CPU A: spin_lock_irqsave(&dev_lock, flags) | ||
36 | CPU A: val = readl(my_status); | ||
37 | CPU A: ... | ||
38 | CPU A: writel(newval, ring_ptr); | ||
39 | CPU A: spin_unlock_irqrestore(&dev_lock, flags) | ||
40 | ... | ||
41 | CPU B: spin_lock_irqsave(&dev_lock, flags) | ||
42 | CPU B: val = readl(my_status); | ||
43 | CPU B: ... | ||
44 | CPU B: writel(newval2, ring_ptr); | ||
45 | CPU B: spin_unlock_irqrestore(&dev_lock, flags) | ||
46 | ... | ||
47 | |||
48 | 上述例子中,设备可能会先接收到newval2的值,然后接收到newval的值,问题就 | ||
49 | 发生了。不过很容易通过下面方法来修复: | ||
50 | |||
51 | ... | ||
52 | CPU A: spin_lock_irqsave(&dev_lock, flags) | ||
53 | CPU A: val = readl(my_status); | ||
54 | CPU A: ... | ||
55 | CPU A: writel(newval, ring_ptr); | ||
56 | CPU A: (void)readl(safe_register); /* 配置寄存器?*/ | ||
57 | CPU A: spin_unlock_irqrestore(&dev_lock, flags) | ||
58 | ... | ||
59 | CPU B: spin_lock_irqsave(&dev_lock, flags) | ||
60 | CPU B: val = readl(my_status); | ||
61 | CPU B: ... | ||
62 | CPU B: writel(newval2, ring_ptr); | ||
63 | CPU B: (void)readl(safe_register); /* 配置寄存器?*/ | ||
64 | CPU B: spin_unlock_irqrestore(&dev_lock, flags) | ||
65 | |||
66 | 在解决方案中,读取safe_register寄存器,触发IO芯片清刷未处理的写操作, | ||
67 | 再处理后面的读操作,防止引发数据不一致问题。 | ||