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From: Markus Armbruster <armbru@redhat.com>
References: <1409115651-3612-1-git-send-email-john.liuli@huawei.com>
Date: Wed, 27 Aug 2014 08:44:45 +0200
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	liuli's message of "Wed, 27 Aug 2014 13:00:51 +0800")
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Subject: Re: [Qemu-devel] [PATCH] qemu-char: fix terminal crash when using
	"-monitor stdio -nographic"
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To: "john.liuli" <john.liuli@huawei.com>
Cc: qemu-devel@nongnu.org, aliguori@amazon.com

"john.liuli" <john.liuli@huawei.com> writes:

> From: Li Liu <john.liuli@huawei.com>
>
> Eeay to reproduce, just try "qemu -monitor stdio -nographic"
> and type "quit", then the terminal will be crashed.
>
> There are two pathes try to call tcgetattr of stdio in vl.c:
>
> 1) Monitor_parse(optarg, "readline");
>    .....
>    qemu_opts_foreach(qemu_find_opts("chardev"),
>                      chardev_init_func, NULL, 1) != 0)
>
> 2) if (default_serial)
>    add_device_config(DEV_SERIAL, "stdio");
>    ....
>    if (foreach_device_config(DEV_SERIAL, serial_parse) < 0)
>
> Both of them will trigger qemu_chr_open_stdio which will disable
> ECHO attributes. First one has updated the attributes of stdio
> by calling qemu_chr_fe_set_echo(chr, false). And the tty
> attributes has been saved in oldtty. Then the second path will
> redo such actions, and the oldtty is overlapped. So till "quit",
> term_exit can't recove the correct attributes.
>
> Signed-off-by: Li Liu <john.liuli@huawei.com>

Yes, failure to restore tty settings is a bug.

But is having multiple character devices use the same terminal valid?
If no, can we catch and reject the attempt?

[...]