Re: dd does not handle input from pipes correctly (coreutils-5.93)

[James Youngman]

On Thu, Nov 17, 2005 at 11:55:42PM -0800, Paul Mielke wrote:

> After I sent the bug report, I realized why it was that we suddenly
> started seeing this problem in a script that had been working for
> quite a while:  we just got a new machine that's a dual cpu box
> and are running an MP linux kernel.  The first write to the pipe
> wakes up the reader and he actually gets to run, instead of hanging
> out to dry on the run queue until the writer fills up the pipe buffer
> and blocks.  On a single cpu machine, you would only see the
> problem very rarely (if an interrupt happens to cause a reschedule
> at just the wrong time).


Many systems now include the 'buffer' program (I have it here on an
Ubuntu box).  If you have it, try piping the data through 'buffer -z
4096' (or whatever PIPE_BUF is on your machine if it's not 4096).

Regards,
James.