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Re: [Bug-tar] opening files with O_NONBLOCK causes problems
From: |
Joerg Schilling |
Subject: |
Re: [Bug-tar] opening files with O_NONBLOCK causes problems |
Date: |
Fri, 06 Jan 2012 15:42:26 +0100 |
User-agent: |
nail 11.22 3/20/05 |
Ron Kerry <address@hidden> wrote:
> Eric -
>
> I discussed this with one of our DMF engineers. He asked me to pass along the
> following message. It
> looks like opening with O_NONBLOCK and then using fcntl() to clear the
> O_NONBLOCK flag will work in
> a DMF context.
>
> - Ron
>
> ----------------
>
> Okay, I wrote a test program to verify the behavior. The other person
> is correct, if you've got a fifo, you need the O_NONBLOCK on the open to
> prevent the hang. My test program did an open with O_NONBLOCK, then did
> an fstat on the fd, and if a fifo, it closed the file. If not a fifo,
> it used fcntl(fd, F_SETFL) to clear the O_NONBLOCK flag before issuing
> the read call. This works correctly for DMF, we get the behavior we
> want. I think it will also do the right thing for leased files. Thanks
> for the help on this!
The main problem in this context is that the behavior for O_NONBLOCK on
non-FIFO files is _unspecified_.
The solution you are currently discussing is specific to the implementation of
your HSM. Other software could have a behavior that would cause other problems
in case you use the solution that works for your HSM.
Jörg
--
EMail:address@hidden (home) Jörg Schilling D-13353 Berlin
address@hidden (uni)
address@hidden (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, (continued)
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Paul Eggert, 2012/01/05
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Joerg Schilling, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Eric Blake, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Joerg Schilling, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Eric Blake, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Joerg Schilling, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Ron Kerry, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Eric Blake, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Kevin Fox, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Ron Kerry, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems,
Joerg Schilling <=
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Eric Blake, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Paul Eggert, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Eric Blake, 2012/01/06
- Re: [Bug-tar] opening files with O_NONBLOCK causes problems, Ron Kerry, 2012/01/10