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author | 2015-08-04 12:17:53 -0700 | |
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committer | 2015-08-04 15:44:42 -0700 | |
commit | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch) | |
tree | 1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/zh_CN/io_ordering.txt | |
parent | 98260f3884f4a202f9ca5eabed40b1354c489b29 (diff) |
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base.
It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:
commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Sat Jul 25 12:13:34 2015 +0200
Prepare v4.1.3-rt3
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.
Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/Documentation/zh_CN/io_ordering.txt')
-rw-r--r-- | kernel/Documentation/zh_CN/io_ordering.txt | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/kernel/Documentation/zh_CN/io_ordering.txt b/kernel/Documentation/zh_CN/io_ordering.txt new file mode 100644 index 000000000..e592daf4e --- /dev/null +++ b/kernel/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 Contact the Chinese maintainer if this translation is outdated +or if there is a problem with the translation.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。 |