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Re: select() hanging after terminal killed

On 29.04.2010 17:21, Christopher Faylor wrote:
On Thu, Apr 29, 2010 at 05:11:00PM +0200, Corinna Vinschen wrote:
On Apr 29 12:53, Thomas Wolff wrote:
If a terminal gets killed, its tty/pty is not properly closed.
This is likely to confuse applications and let them hang, as observed
with mined (thanks Andy for the report) and joe.

On Linux and SunOS, a subsequent read() return 0 (indicating EOF);
any further read() returns -1, errno indicating EIO.
Immediate write() may report success a few times,
further write() returns -1, errno indicating EIO.

On Linux, select() indicates an exception and EIO.
On SunOS, select() indicates both an exception and input (weird),
and ENOENT initially, EIO on further attempts.

On Cygwin, the following is observed:
* EOF is not signalled on read(); rather EIO is indicated right away.
   (Maybe not too bad, an application can handle that as well.)
* select() with timeout hangs.

Especially the latter can hardly be handled by an application.
Can you create a simple testcase?
I finally managed it... (attached).
In a mintty or xterm, run hupsel > /dev/tty... (some other terminal to observe).
Then close the terminal (click on 'X' corner).
On Linux, the program terminates.
On cygwin, the program hangs in select().

Hmm.  Since the owner has both sides of the pipe open maybe closing the
slave side doesn't trigger select.

It's possible that Corinna's changes to tty handling might make this
work better.  It would be interesting to see how this works in a recent
Unfortunately not.

Kind regards,

Attachment: hupsel.c
Description: Text document

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