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68 lines
2.9 KiB
68 lines
2.9 KiB
Chinese translated version of Documentation/driver-api/io_ordering.rst |
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If you have any comment or update to the content, please contact the |
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original document maintainer directly. However, if you have a problem |
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communicating in English you can also ask the Chinese maintainer for |
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help. Contact the Chinese maintainer if this translation is outdated |
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or if there is a problem with the translation. |
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Traditional Chinese maintainer: Hu Haowen <[email protected]> |
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Documentation/driver-api/io_ordering.rst 的繁體中文翻譯 |
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如果想評論或更新本文的內容,請直接聯繫原文檔的維護者。如果你使用英文 |
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交流有困難的話,也可以向繁體中文版維護者求助。如果本翻譯更新不及時或 |
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者翻譯存在問題,請聯繫繁體中文版維護者。 |
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繁體中文版維護者: 胡皓文 Hu Haowen <[email protected]> |
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繁體中文版翻譯者: 胡皓文 Hu Haowen <[email protected]> |
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繁體中文版校譯者: 胡皓文 Hu Haowen <[email protected]> |
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以下爲正文 |
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在某些平台上,所謂的內存映射I/O是弱順序。在這些平台上,驅動開發者有責任 |
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保證I/O內存映射地址的寫操作按程序圖意的順序達到設備。通常讀取一個「安全」 |
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設備寄存器或橋寄存器,觸發IO晶片清刷未處理的寫操作到達設備後才處理讀操作, |
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而達到保證目的。驅動程序通常在spinlock保護的臨界區退出之前使用這種技術。 |
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這也可以保證後面的寫操作只在前面的寫操作之後到達設備(這非常類似於內存 |
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屏障操作,mb(),不過僅適用於I/O)。 |
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假設一個設備驅動程的具體例子: |
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... |
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CPU A: spin_lock_irqsave(&dev_lock, flags) |
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CPU A: val = readl(my_status); |
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CPU A: ... |
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CPU A: writel(newval, ring_ptr); |
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CPU A: spin_unlock_irqrestore(&dev_lock, flags) |
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... |
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CPU B: spin_lock_irqsave(&dev_lock, flags) |
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CPU B: val = readl(my_status); |
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CPU B: ... |
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CPU B: writel(newval2, ring_ptr); |
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CPU B: spin_unlock_irqrestore(&dev_lock, flags) |
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... |
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上述例子中,設備可能會先接收到newval2的值,然後接收到newval的值,問題就 |
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發生了。不過很容易通過下面方法來修復: |
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... |
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CPU A: spin_lock_irqsave(&dev_lock, flags) |
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CPU A: val = readl(my_status); |
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CPU A: ... |
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CPU A: writel(newval, ring_ptr); |
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CPU A: (void)readl(safe_register); /* 配置寄存器?*/ |
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CPU A: spin_unlock_irqrestore(&dev_lock, flags) |
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... |
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CPU B: spin_lock_irqsave(&dev_lock, flags) |
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CPU B: val = readl(my_status); |
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CPU B: ... |
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CPU B: writel(newval2, ring_ptr); |
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CPU B: (void)readl(safe_register); /* 配置寄存器?*/ |
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CPU B: spin_unlock_irqrestore(&dev_lock, flags) |
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在解決方案中,讀取safe_register寄存器,觸發IO晶片清刷未處理的寫操作, |
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再處理後面的讀操作,防止引發數據不一致問題。 |
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