Messages in this thread | | | Date | Tue, 23 Sep 2003 00:33:57 -0700 | From | "David S. Miller" <> | Subject | Re: how is recv(..., MSG_PEEK) racy? |
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On Tue, 23 Sep 2003 12:15:45 +0530 Abhijit Menon-Sen <ams@wiw.org> wrote:
> While fetchmail doesn't seem to be triggering that printk(), I'm curious > about what the race condition is. Google found a post by DaveM saying it > has something to do with URG data, but without any further details. I'd > appreciate any explanation of the problem(s).
If multiple threads do reads to the same socket, one using MSG_PEEK and one without, there is a race because the thread doing MSG_PEEK doesn't expect the bytes it is "peeking" at to be removed from the receive queue from the socket, but that is exactly what the other thread will do.
When using URG data, the kernel becomes the "other thread doing non-MSG_PEEK reads" on the socket. So if you use MSG_PEEK and URG data at the same time, you will likely trigger the race and that printk() alerting you to this fact. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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