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| author |   Dmitry Safonov <dima@arista.com> | 2018-11-01 00:24:48 +0000 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 12:16:33 +0100 |
| commit | c96cf923a98d1b094df9f0cf97a83e118817e31b (patch) | |
| tree | 600f4d868ef87ff58a642bb7e6d4825894d9c657 /include/linux/tty.h | |
| parent | tty: Hold tty_ldisc_lock() during tty_reopen() (diff) | |
| download | wireguard-linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.tar.xz wireguard-linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.zip | |
tty: Don't block on IO when ldisc change is pending
There might be situations where tty_ldisc_lock() has blocked, but there
is already IO on tty and it prevents line discipline changes.
It might theoretically turn into dead-lock.
Basically, provide more priority to pending tty_ldisc_lock() than to
servicing reads/writes over tty.
User-visible issue was reported by Mikulas where on pa-risc with
Debian 5 reboot took either 80 seconds, 3 minutes or 3:25 after proper
locking in tty_reopen().
Cc: Jiri Slaby <jslaby@suse.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/tty.h')
| -rw-r--r-- | include/linux/tty.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 414db2bce715..80ae5528ef8e 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -366,6 +366,7 @@ struct tty_file_private { #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ #define TTY_HUPPED 18 /* Post driver->hangup() */ #define TTY_HUPPING 19 /* Hangup in progress */ +#define TTY_LDISC_CHANGING 20 /* Change pending - non-block IO */ #define TTY_LDISC_HALTED 22 /* Line discipline is halted */ /* Values for tty->flow_change */ @@ -383,6 +384,12 @@ static inline void tty_set_flow_change(struct tty_struct *tty, int val) smp_mb(); } +static inline bool tty_io_nonblock(struct tty_struct *tty, struct file *file) +{ + return file->f_flags & O_NONBLOCK || + test_bit(TTY_LDISC_CHANGING, &tty->flags); +} + static inline bool tty_io_error(struct tty_struct *tty) { return test_bit(TTY_IO_ERROR, &tty->flags); |