* Re: Splice on blocking TCP sockets again..
[not found] ` <4AC2F3E4.5000904@gmail.com>
@ 2009-10-01 22:17 ` Jason Gunthorpe
0 siblings, 0 replies; only message in thread
From: Jason Gunthorpe @ 2009-10-01 22:17 UTC (permalink / raw)
To: Eric Dumazet; +Cc: netdev, David S. Miller, Volker Lendecke, linux-kernel
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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