Grant Grundler wrote:
On Fri, Jan 30, 2009 at 3:50 PM, Mark Lord <liml@xxxxxx> wrote:
..
if (likely(last_sg)) last_sg->flags_size |= cpu_to_le32(EPRD_FLAG_END_OF_TBL); + mb(); /* ensure data structure is visible to the chipset */It's not obvious to me what you are racing against here. Normally the mb() is to prevent the above store from getting executed *after* some MMIO read or write that would tell the chip to read the flags_size field (or anything recently stored in that data structure). I guess I'm asking for the comment to indicate which MMIO write it's racing with.
.. It's exactly the same as the generic routine in libata-sff, which has a mb() in the same place for the same reason: To ensure the PRD table is visible to the chipset before we trigger the I/O operation. Pretty standard. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
