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SubjectRe: [patch] updates for the pipe code
Manfred Spraul writes:
> Richard Gooch wrote:
> > What about the problem I
> > reported back on 16-FEB? It's still happening with 2.3.48. The problem
> > does not occur with 2.2.14.
> >
> > > Hi, all. I've been noticing odd behaviour with named pipes under
> > > recent 2.3.x kernels (at least since 2.3.36 and possibly before).
> > >
> > > If you open a FIFO with O_RDONLY and then call read(2), and then
> > > another process writes to the FIFO, the read(2) call doesn't return. A
> > > subsequent writer process does wake up the reader, however.
> > >
> > > Has anybody else noticed this behaviour?
> >
> > I've noticed this problem on UP and SMP systems. It doesn't always
> > happen, but it *does* happen :-(
> >
> Hmm.
> I didn't notice a bug when I rewrote the locking.
> Do you have a test application? Is someone using O_NONBLOCK, which end
> of the fifo is opened first?

I don't really have a test application. It's my shell scripts for
synchronising my window manager and X client. The reader is cat and
the writer is tcsh/echo.

No-one should be doing O_NONBLOCK. I don't really know which is
starting first. Earlier in 2.3.4x I had some testcode which sometimes
demonstrated the same problem, but that testcode hasn't failed yet
with 2.3.48.

Not once have I seen the problem with 2.2.14.



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