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Date: Tue, 15 Dec 2009 17:45:27 -0800 From: Earl Chew <earl_chew@...lent.com> To: "Hans J. Koch" <hjk@...utronix.de> CC: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, gregkh@...e.de, linux-mm <linux-mm@...ck.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH 1/1] Userspace I/O (UIO): Add support for userspace DMA Hans J. Koch wrote: > No, dma-mem would be a directory containing some more attributes. Maybe one > called "create" that allocates a new buffer. > [ .. snip ..] > Writing the size to that supposed "create" attribute could allocate the > buffer and and create more attributes that contain the information you need. Hmm ... I can't see how to make this into a transaction. Suppose two threads write to /sys/.../create simultaneously (or very close together) and further suppose that each call succeeds. It's not clear to me how each can figure out where to find the outcome of its operation because write() doesn't return anything other than the number of octets written. Writing "id, size" might work, but sorting out a good enough id might be a little clunky. A process id wouldn't be good enough (with different threads), and a thread id might get recycled. Any other ideas ? Earl -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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