Messages in this thread | | | Date | Thu, 1 Oct 2009 16:17:06 -0600 | From | Jason Gunthorpe <> | Subject | Re: Splice on blocking TCP sockets again.. |
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On Wed, Sep 30, 2009 at 08:00:04AM +0200, Eric Dumazet wrote:
> >> I admit I don't understand why SPLICE_F_NONBLOCK exists, it seems very > >> un-unixy to have a syscall completely ignore the NONBLOCK flag of the > >> fd it is called on. Ie setting NONBLOCK on the pipe itself does > >> nothing when using splice.. > > > > Hmm, good question, I dont have the answer but I'll digg one. > > > > commit 29e350944fdc2dfca102500790d8ad6d6ff4f69d > splice: add SPLICE_F_NONBLOCK flag > > It doesn't make the splice itself necessarily nonblocking (because the > actual file descriptors that are spliced from/to may block unless they > have the O_NONBLOCK flag set), but it makes the splice pipe operations > nonblocking. > > Signed-off-by: Linus Torvalds <torvalds@osdl.org> > > See Linus intention was pretty clear : O_NONBLOCK should be taken > into account by 'actual file that are spliced from/to', regardless > of SPLICE_F_NONBLOCK flag
Yes, that seems reasonable.
What confuses me is that if O_NONBLOCK is set on the _pipe_ and SPICE_F_NONBLOCK is not set on the splice call the splice still blocks - that is unlike other unix apis, eg MSG_DONTWAIT
It seems to me that SPICE_F_NONBLOCK should be or'd with O_NONBLOCK on the pipe?
Thanks, Jason
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