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While using emacs, cat or others' commands in konsole with recent kernels, I have met many times that CTRL-C freeze konsole. After konsole freeze I can't type anything, then I have to open a new one, it is very annoying. See bug report: https://bugs.kde.org/show_bug.cgi?id=175283 The platform in that bug report is Solaris, but now the pty in linux has the same problem or the same behavior as Solaris :) It has high possibility to trigger the problem follow steps below: Note: In my test, BigFile is a text file whose size is bigger than 1G 1:open konsole 1:cat BigFile 2:CTRL-C After some digging, I find out the reason is that commit 1d1d14da12e7 ("pty: Fix buffer flush deadlock") changes the behavior of pty_flush_buffer. Thread A Thread B -------- -------- 1:n_tty_poll return POLLIN 2:CTRL-C trigger pty_flush_buffer tty_buffer_flush n_tty_flush_buffer 3:attempt to check count of chars: ioctl(fd, TIOCINQ, &available) available is equal to 0 4:read(fd, buffer, avaiable) return 0 5:konsole close fd Yes, I know we could use the same patch included in the BUG report as a workaround for linux platform too. But I think the data in ldisc is belong to application of another side, we shouldn't clear it when we want to flush write buffer of this side in pty_flush_buffer. So I think it is better to disable ldisc flush in pty_flush_buffer, because its new hehavior bring no benefit except that it mess up the behavior between POLLIN, and TIOCINQ or FIONREAD. Also I find no flush_buffer function in others' tty driver has the same behavior as current pty_flush_buffer. Fixes: 1d1d14da12e7 ("pty: Fix buffer flush deadlock") CC: stable@vger.kernel.org # v4.0+ Signed-off-by: Wang YanQing <udknight@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.