.  Finally, process 3 does a write which blocks on the
process 2's ldisc reference.

This patch does introduce some changes in semantics.  For example, a line
discipline change on side 'a' of a ptmx/pty pair, will now wait for a
read/write to complete on the other side, or side 'b'.  The current behavior
is to simply wait for any read/writes on only side 'a', not both sides 'a' and
'b'.  I think this behavior makes sense, but I wanted to point it out.

I've tested the patch with a bunch of read/write/poll while changing the line
discipline out from underneath.

This patch obviates the need for the above "hide the problem" patch.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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