Messages in this thread | | | Date | Thu, 21 Dec 2000 22:26:00 -0600 (CST) | From | Paul Cassella <> | Subject | Re: [RFC] Semaphores used for daemon wakeup |
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On Fri, 22 Dec 2000, Daniel Phillips wrote:
> But isn't this actually a simple situation? How about:
I had only adapted that example because it had already been posted showing one way to do it, and so provided something to compare the sv approach to.
> dmabuf_alloc(...) > { > while (1) { > spin_lock(&dmabuf_lock); > attempt to grab a free buffer; > spin_unlock(&dmabuf_lock); > if (success) > return; > down(&dmabuf_wait); > } > }
> dmabuf_free(...) > { > spin_lock(&dmabuf_lock); > free up buffer; > spin_unlock(&dmabuf_lock); > up(&dmabuf_wait); > }
This does things a little differently than the way the original did it. I thought the original implied that dmabuf_free() might free up multiple buffers. There's no indication in the comments that this is the case, but the original, by using vall_sema(), wakes up all dmabuf_alloc()'s that had gone to sleep.
The example wasn't meant to be an ideal use of sv's, but merely as an example of how they could be used to achieve the same behavior as the code that was posted.
-- Paul Cassella pwc@sgi.com
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