Re: Read/write counts

[Joel Becker <Joel.Becker@oracle.com>]

On Mon, Jun 04, 2007 at 08:57:16PM +0200, Roman Zippel wrote:
> On Mon, 4 Jun 2007, Theodore Tso wrote:
> 
> > Hmm, I'm not sure I would go that far.  Per the POSIX specification,
> > we support the optional BSD-style restartable system calls for signals
> > which will avoid short reads; but this is only true if SA_RESTART is
> > passed to sigaction().  Without SA_RESTART, we will indeed return
> > short reads, as required by POSIX.
> > 
> > I don't think Linus has said that short reads are always evil; I
> > certainly can't remember him ever making that statement.  Do you have
> > a pointer to a LKML message where he's said that?
> 
> That's the last discussion about signals and I/O I can remember:
> http://www.ussg.iu.edu/hypermail/linux/kernel/0208.0/0188.html

	He said 'disk read', not 'read(2)'.  I'd expect he means certain
things like stat(2) and readdir(2) when they have to go to disk.
read(2) explicitly lists EINTR as a valid result, and often folks use
signals to interrupt read(2).  The world certainly writes programs
to expect short read(2).

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127