tty: Fix pty master poll() after slave closes v2
Commit f95499c3 ("n_tty: Don't wait for buffer work in read() loop") introduces a race window where a pty master can be signalled that the pty slave was closed before all the data that the slave wrote is delivered. Commit f8747d4a ("tty: Fix pty master read() after slave closes") fixed the problem in case of n_tty_read, but the problem still exists for n_tty_poll. This can be seen by running 'for ((i=0; i<100;i++));do ./test.py ;done' where test.py is: import os, select, pty (pid, pty_fd) = pty.fork() if pid == 0: os.write(1, 'This string should be received by parent') else: poller = select.epoll() poller.register( pty_fd, select.EPOLLIN ) ready = poller.poll( 1 * 1000 ) for fd, events in ready: if not events & select.EPOLLIN: print 'missed POLLIN event' else: print os.read(fd, 100) poller.close() The string from the slave is missed several times. This patch takes the same approach as the fix for read and special cases this condition for poll. Tested on 3.16. Signed-off-by:Francesco Ruggeri <fruggeri@arista.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
7e12e675
Please register or sign in to comment