[PATCH] POLL_OUT for tty drivers, misc bug

From: Sapan J . Bhatia (lists@corewars.org)
Date: Thu Mar 21 2002 - 11:57:47 EST


Hello,

While fixing a flow control bug that truncated output to a terminal in
User Mode Linux, I noticed that the tty drivers only send POLL_IN on new
data being available but not POLL_OUT when the device is ready for new
data.

This patch fixes the bug in the line discipline and the pty driver.

Also, there's another minor bug in n_tty.c where write_chan returns
on a (retvalue < 0) unconditionally. This is a problem, since the type of
IO (BLOCKING / NON_BLOCKING) is stored in the tty, and if the console driver
returns a -EAGAIN (eg. in UML on getting an EAGAIN from the host kernel),
write_chan returns even in the case of a blocking write, which is wrong
since the process doesn't expect it.

Regards,
Sapan
 



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