diff options
author | Lin Yongting <linyongting@gmail.com> | 2014-04-16 23:25:28 +0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-16 14:13:26 -0700 |
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 @@ +Chinese translated version of Documentation/io_orderings.txt + +If you have any comment or update to the content, please contact the +original document maintainer directly. However, if you have a problem +communicating in English you can also ask the Chinese maintainer for +help. Contact the Chinese maintainer if this translation is outdated +or if there is a problem with the translation. + +Chinese maintainer: Lin Yongting <linyongting@gmail.com> +--------------------------------------------------------------------- +Documentation/io_ordering.txt 的中文翻译 + +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 +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 +译存在问题,请联系中文版维护者。 + +中文版维护者: 林永听 Lin Yongting <linyongting@gmail.com> +中文版翻译者: 林永听 Lin Yongting <linyongting@gmail.com> +中文版校译者: 林永听 Lin Yongting <linyongting@gmail.com> + + +以下为正文 +--------------------------------------------------------------------- + +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 +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” +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, +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。 +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 +屏障操作,mb(),不过仅适用于I/O)。 + +假设一个设备驱动程的具体例子: + + ... +CPU A: spin_lock_irqsave(&dev_lock, flags) +CPU A: val = readl(my_status); +CPU A: ... +CPU A: writel(newval, ring_ptr); +CPU A: spin_unlock_irqrestore(&dev_lock, flags) + ... +CPU B: spin_lock_irqsave(&dev_lock, flags) +CPU B: val = readl(my_status); +CPU B: ... +CPU B: writel(newval2, ring_ptr); +CPU B: spin_unlock_irqrestore(&dev_lock, flags) + ... + +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 +发生了。不过很容易通过下面方法来修复: + + ... +CPU A: spin_lock_irqsave(&dev_lock, flags) +CPU A: val = readl(my_status); +CPU A: ... +CPU A: writel(newval, ring_ptr); +CPU A: (void)readl(safe_register); /* 配置寄存器?*/ +CPU A: spin_unlock_irqrestore(&dev_lock, flags) + ... +CPU B: spin_lock_irqsave(&dev_lock, flags) +CPU B: val = readl(my_status); +CPU B: ... +CPU B: writel(newval2, ring_ptr); +CPU B: (void)readl(safe_register); /* 配置寄存器?*/ +CPU B: spin_unlock_irqrestore(&dev_lock, flags) + +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, +再处理后面的读操作,防止引发数据不一致问题。 |