Messages in this thread | | | From | "Hua Zhong" <> | Subject | RE: UDP recvmsg blocks after select(), 2.6 bug? | Date | Sun, 17 Oct 2004 12:21:38 -0700 |
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> > This is a distraction. If the call to select() had been substituted > > with a call to recvmsg(), it would have blocked. Instead, > select() is > > returning 'yes, you can read', and then recvmsg() is blocking. The > > select() lied. The information is all sitting in the kernel packet > > No. A million things might happen between select() and recvmsg(), both > in kernel and application. For a consistent behaviour throughout all > possibilities, you *have* to assume that any read on a blocking fd may > block.
Care to provide a real example?
UDP isn't one. It was done for performance reasons as David admitted and it could very well be done otherwise: do the checksum before select returns.
David has admitted the only reason Linux chose to do so is performance.
It might be the case that a million things might happen between select and recvmsg, but none of them, as I can see, *have* to force Linux to work this way. The only reason as I can see is performance and imlementation convenience.
Hua
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