Since at least before 2.6.30, it has not been possible to observe
a hung up file pointer in a tty driver's open() method unless/until
the driver open() releases the tty_lock() (eg., before blocking).
This is because tty_open() adds the file pointer while holding
the tty_lock() _and_ doesn't release the lock until after calling
the tty driver's open() method. [ Before tty_lock(), this was
lock_kernel(). ]
Since __tty_hangup() first waits on the tty_lock() before
enumerating and hanging up the open file pointers, either
__tty_hangup() will wait for the tty_lock() or tty_open() will
not yet have added the file pointer. For example,
CPU 0 | CPU 1
|
tty_open | __tty_hangup
.. | ..
tty_lock | ..
tty_reopen | tty_lock / blocks
.. |
tty_add_file(tty, filp) |
.. |
tty->ops->open(tty, filp) |
tty_port_open |
tty_port_block_til_ready |
.. |
while (1) |
.. |
tty_unlock | / unblocks
schedule | for each filp on tty->tty_files
| f_ops = tty_hung_up_fops;
| ..
| tty_unlock
tty_lock |
.. |
tty_unlock |
Note that since tty_port_block_til_ready() and similar drop
the tty_lock while blocking, when woken, the file pointer
must then be tested for having been hung up.
Also, fix bit-rotted drivers that used extra_count to track the
port->count bump.
CC: Mikael Starvik <starvik@axis.com>
CC: Samuel Ortiz <samuel@sortiz.org>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty->closing informs the line discipline that the hardware will
be shutting down imminently, and to disable further input other
than soft flow control (but to still allow additional output).
However, the tty lock is the necessary lock for preventing
concurrent changes to tty->closing. As shown by the call-tree
audit [1] of functions that modify tty->closing, the tty lock
is already held for those functions.
[1]
Call-tree audit of functions that modify tty->closing
* does not include call tree to tty_port_close(), tty_port_close_start(),
or tty_port_close_end() which is already documented in
'tty: Document locking for tty_port_close{,start,end}' that shows
callers to those 3 functions hold the tty lock
tty_release()
tty->ops->close() --+
|
__tty_hangup() |
tty->ops->close() --+
|
mp_close():drivers/staging/sb105x/sb_pci_mp.c
dngc_tty_close():drivers/staging/dgnc/dgnc_tty.c
dgap_tty_close():drivers/staging/dgap/dgap_tty.c
dgrp_tty_close():drivers/staging/dgrp/dgrp_tty.c
rp_close():drivers/tty/rocket.c
hvsi_close():drivers/tty/hvc/hvsi.c
rs_close():drivers/tty/serial/68328serial.c
rs_close():drivers/tty/serial/crisv10.c
uart_close():drivers/tty/serial/serial_core.c
isdn_tty_close():drivers/isdn/i4l/isdn_tty.c
tty3215_close():drivers/s390/char/con3215.c
tty_open()
tty_ldisc_setup() ----+
|
__tty_hangup() |
tty_ldisc_hangup() ---+
|
tty_set_ldisc() --------+
tty_ldisc_restore() --+
|
+- tty_ldisc_open()
ld->ops->open() --+
|
+- n_tty_open()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty lock is held when the tty driver's hangup() method is called
(from the lone call-site, __tty_hangup()). The call-tree audit [1]
of tty_port_hangup() is a closed graph of the callers of
tty_port_hangup(); ie., all callers originate only from __tty_hangup().
Of these callers, none drop the tty lock prior to calling
tty_port_hangup().
[1]
Call-tree audit of tty_port_hangup()
__tty_hangup()
tty->ops->hangup() --+
|
rs_hangup():arch/ia64/hp/sim/simserial.c
line_hangup():arch/um/drivers/line.c
gdm_tty_hangup():drivers/staging/gdm724x/gdm_tty.c
fwtty_hangup():drivers/staging/fwserial/fwserial.c
acm_tty_hangup():drivers/usb/class/cdc-acm.c
serial_hangup():drivers/usb/serial/usb-serial.c
ipoctal_hangup():drivers/ipack/devices/ipoctal.c
cy_hangup():drivers/tty/cyclades.c
isicom_hangup():drivers/tty/isicom.c
rp_hangup():drivers/tty/rocket.c
dashtty_hangup():drivers/tty/metag_da.c
moxa_hangup():drivers/tty/moxa.c
gsmtty_hangup():drivers/tty/n_gsm.c
goldfish_tty_hangup():drivers/tty/goldfish.c
ehv_bc_tty_hangup():drivers/tty/ehv_bytechan.c
mxser_hangup():drivers/tty/mxser.c
kgdb_nmi_tty_hangup():drivers/tty/serial/kgdb_nmi.c
ifx_spi_hangup():drivers/tty/serial/ifx6x60.c
ntty_hangup():drivers/tty/nozomi.c
capinc_tty_hangup():drivers/isdn/capi/capi.c
mgslpc_hangup():drivers/char/pcmcia/synclink_cs.c
sdio_uart_hangup():drivers/mmc/card/sdio_uart.c
rfcomm_tty_hangup():net/bluetooth/rfcomm/tty.c
|
+- tty_port_hangup()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty lock is held when the tty driver's open() method is called
(from tty_open()). The call-tree audit [1] of tty_port_block_til_ready()
is a closed graph of the callers of tty_port_block_til_ready();
ie., all callers originate only from tty_open().
Of these callers, none drop the tty lock.
Also, document tty_port_block_til_ready() may drop and reacquire
the tty lock when blocking, which means the tty or tty_port may have
changed state.
[1]
Call-tree audit of tty_port_block_til_ready()
* does not include call tree of tty_port_open() which is already
documented in 'tty: Document locking from tty_port_open()'
tty_open()
tty->ops->open() --+
|
cy_open():drivers/tty/cyclades.c
rp_open():drivers/tty/rocket.c
rs_open():drivers/tty/amiserial.c
moxa_open():drivers/tty/moxa.c
gsmtty_open():drivers/tty/n_gsm.c
rs_open():drivers/tty/serial/68328serial.c
uart_open():drivers/tty/serial/serial_core.c
isdn_tty_open():drivers/isdn/i4l/isdn_tty.c
mgslpc_open():drivers/char/pcmcia/synclink_cs.c
|
+- tty_port_block_til_ready()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty lock is held when the tty driver's open method is called
(from the lone call-site, tty_open()). The call-tree audit [1] of
tty_port_open() is a closed graph of the callers of tty_port_open();
ie., all callers originate from only tty_open().
Of these callers, none drop the tty lock.
Also, document that tty_port_block_til_ready() may drop and reacquire
the tty lock when blocking, which means the tty or tty_port may have
changed state.
[1]
Call-tree audit of tty_port_open()
tty_open()
tty->ops->open() --+
|
rs_open():arch/ia64/hp/sim/simserial.c
*line_open():arch/um/drivers/line.c
gdm_tty_open():drivers/staging/gdm724x/gdm_tty.c
fwtty_open():drivers/staging/fwserial/fwserial.c
acm_tty_open():drivers/usb/class/cdc-acm.c
serial_open():drivers/usb/serial/usb-serial.c
pti_tty_driver_open():drivers/misc/pti.c
ipoctal_open():drivers/ipack/devices/ipoctal.c
isicom_open():drivers/tty/isicom.c
dashtty_open():drivers/tty/metag_da.c
goldfish_tty_open():drivers/tty/goldfish.c
ehv_bc_tty_open():drivers/tty/ehv_bytechan.c
mxser_open():drivers/tty/mxser.c
kgdb_nmi_tty_open():drivers/tty/serial/kgdb_nmi.c
ifx_spi_open():drivers/tty/serial/ifx6x60.c
smd_tty_open():drivers/tty/serial/msm_smd_tty.c
ntty_open():drivers/tty/nozomi.c
capinc_tty_open():drivers/isdn/capi/capi.c
tpk_open():drivers/char/ttyprintk.c
sdio_uart_open():drivers/mmc/card/sdio_uart.c
rfcomm_tty_open():net/bluetooth/rfcomm/tty.c
|
+- tty_port_open()
* line_open() is the .open method for 2 um drivers
declared in ./arch/um/drivers/stdio_console.c and
in ./arch/um/drivers/ssl.c, and not called directly
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty lock is held when the tty driver's .close method is called
(from the two lone call-sites of tty_release() and __tty_hangup()).
The call-tree audit[1] of tty_port_close(), tty_port_close_start,
and tty_port_close_end() is a closed graph of the callers of these
3 functions; ie., all callers originate from only tty_release()
or __tty_hangup().
Of these callers, none drop the tty lock.
Also, document tty_port_close_start() may drop and reacquire the
tty lock in tty_wait_until_sent_from_close(), which means the tty
or tty_port may have changed state (but not reopened or hung up).
[1]
Call-tree audit of tty_port_close, tty_port_close_start, and tty_port_close_end()
tty_release()
tty->ops->close() --+
|
__tty_hangup() |
tty->ops->close() --+
|
+- rp_close():drivers/tty/rocket.c -------------------+
+- uart_close():drivers/tty/serial/serial_core.c -----+
| +- tty_port_close_start()
|
|
+- close():drivers/tty/synclinkmp.c ------------------+
+- rs_close():drivers/tty/amiserial.c ----------------+
+- gsmtty_close():drivers/tty/n_gsm.c ----------------+
+- mxser_close():drivers/tty/mxser.c -----------------+
+- close():drivers/tty/synclink_gt.c -----------------+
+- mgsl_close():drivers/tty/synclink.c ---------------+
+- isdn_tty_close():drivers/isdn/i4l/isdn_tty.c ------+
+- mgslpc_close():drivers/char/pcmcia/synclink_cs.c --+
+- ircomm_tty_close():net/irda/ircomm/ircomm_tty.c ---+
| |
rs_close():arch/ia64/hp/sim/simserial.c |
*line_close():arch/um/drivers/line.c |
gdm_tty_close():drivers/staging/gdm724x/gdm_tty.c
fwtty_close():drivers/staging/fwserial/fwserial.c
acm_tty_close():drivers/usb/class/cdc-acm.c
serial_close():drivers/usb/serial/usb-serial.c
pti_tty_driver_close():drivers/misc/pti.c
ipoctal_close():drivers/ipack/devices/ipoctal.c
cy_close():drivers/tty/cyclades.c
isicom_close():drivers/tty/isicom.c
dashtty_close():drivers/tty/metag_da.c
moxa_close():drivers/tty/moxa.c
goldfish_tty_close():drivers/tty/goldfish.c
ehv_bc_tty_close():drivers/tty/ehv_bytechan.c
kgdb_nmi_tty_close():drivers/tty/serial/kgdb_nmi.c
ifx_spi_close():drivers/tty/serial/ifx6x60.c
smd_tty_close():drivers/tty/serial/msm_smd_tty.c
ntty_close():drivers/tty/nozomi.c
capinc_tty_close():drivers/isdn/capi/capi.c
tpk_close():drivers/char/ttyprintk.c
sdio_uart_close():drivers/mmc/card/sdio_uart.c |
rfcomm_tty_close():net/bluetooth/rfcomm/tty.c |
| |
+- tty_port_close():drivers/tty/tty_port.c -----------+
|
+- tty_port_close_start()
+- tty_port_close_end()
* line_close() is the .close method for 2 um drivers,
declared in ./arch/um/drivers/stdio_console.c and
in ./arch/um/drivers/ssl.c, and not called directly
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
None of these files are actually using any __init type directives
and hence don't need to include <linux/init.h>. Most are just a
left over from __devinit and __cpuinit removal, or simply due to
code getting copied from one driver to the next.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Although originally conceived as a hook for port drivers to know
when a port reference is dropped, no driver uses this method.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If the tty driver mistakenly drops the last port reference
before the tty has been released, issue a diagnostic and
abort the port destruction.
This will leak memory and may zombify the port, but might
otherwise keep the machine in runnable state.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function tty_port_tty_hangup() could leak a reference to the tty_struct:
struct tty_struct *tty = tty_port_tty_get(port);
if (tty && (!check_clocal || !C_CLOCAL(tty))) {
tty_hangup(tty);
tty_kref_put(tty);
}
If tty != NULL and the second condition is false we never call tty_kref_put and
the reference is leaked.
Fix by always calling tty_kref_put() which accepts a NULL argument.
The patch fixes a regression introduced by commit aa27a094.
Acked-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Gianluca Anzolin <gianluca@sottospazio.it>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Cc: stable <stable@vger.kernel.org> # 3.10
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Waiting for buffer work to complete is not required for safely
performing changes to the line discipline, once the line discipline
is halted. The buffer work routine, flush_to_ldisc(), will be
unable to acquire an ldisc ref and all existing references were
waited until released (so it can't already have one).
Ensure running buffer work which may reference the soon-to-be-gone
tty completes and any buffer work running after this point retrieves
a NULL tty.
Also, ensure all buffer work is cancelled on port destruction.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Make sure we do not make tty-driver callbacks or wait for port to drain
on uninitialised ports (e.g. when open failed) in
tty_port_close_start().
No callback, such as flush_buffer or wait_until_sent, needs to be made
on a port that has never been opened. Neither does it make much sense to
add drain delay for an uninitialised port.
Currently a drain delay of up to two seconds could be added when a tty
fails to open.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move port drain-delay handling to a separate function.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move HUPCL handling to port shutdown so that DTR is dropped also on hang
up (tty_port_close is a noop for hung-up ports).
Also do not try to drop DTR for uninitialised ports where it has never
been raised (e.g. after a failed open).
Note that this is also the current behaviour of serial-core.
Nine drivers currently call tty_port_close_start directly (rather than
through tty_port_close) and seven of them lower DTR as part of their
close (if the port has been initialised). Fixup the remaining two
drivers so that it continues to be lowered also on normal (non-HUP)
close. [ Note that most of those other seven drivers did not expect DTR
to have been dropped by tty_port_close_start in the first place. ]
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Make sure to check ASYNC_INITIALISED before raising DTR when waking up
from blocked open in tty_port_block_til_ready.
Currently DTR could get raised at hang up as a blocked process would
raise DTR unconditionally before checking for hang up and returning.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move wake up of processes on blocked-open and modem-status wait queues
to after port shutdown at hangup.
This way the woken up processes can use the ASYNC_INITIALIZED flag to
detect port shutdown.
Note that this is the order currently used by serial-core.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Untangle port-shutdown logic and make sure the initialised flag is
always cleared for non-console ports.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It allows for cleaning up on a considerable amount of places. They did
port_get, hangup, kref_put. Now the only thing needed is to call
tty_port_tty_hangup which does exactly that. And they can also decide
whether to consider CLOCAL or completely ignore that.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It allows for cleaning up on a considerable amount of places. They did
port_get, wakeup, kref_put. Now the only thing needed is to call
tty_port_tty_wakeup which does exactly that.
One exception is ifx6x60 where tty_wakeup was open-coded. We now call
tty_wakeup properly there.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After commit "TTY: move tty buffers to tty_port", the tty buffers are
not freed in some drivers. This is because tty_port_destructor is not
called whenever a tty_port is freed. This was an assumption I counted
with but was unfortunately untrue.
Those using refcounting are safe now, but for those which do not we
introduce a function to be called right before the tty_port is freed
by the drivers.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After commit "TTY: move tty buffers to tty_port", the tty buffers are
not freed in some drivers. This is because tty_port_destructor is not
called whenever a tty_port is freed. This was an assumption I counted
with but was unfortunately untrue. So fix the drivers to fulfil this
assumption.
PTY is one of those, here we just need to use tty_port_put instead of
kfree. (Assuming tty_port_destructor does not need port->ops to be set
which we change here too.)
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
So this is it. The big step why we did all the work over the past
kernel releases. Now everything is prepared, so nothing protects us
from doing that big step.
| | \ \ nnnn/^l | |
| | \ / / | |
| '-,.__ => \/ ,-` => | '-,.__
| O __.´´) ( .` | O __.´´)
~~~ ~~ `` ~~~ ~~
The buffers are now in the tty_port structure and we can start
teaching the buffer helpers (insert char/string, flip etc.) to use
tty_port instead of tty_struct all around.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Added tty_device_create_release() and bound to dev->release in
tty_register_device_attr().
Added tty_port_register_device_attr() and used in uart_add_one_port()
instead of tty_register_device_attr().
Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This is for those drivers which do not have dynamic device creation
(do not call tty_port_register_device) and do not want to implement
tty->ops->install (will not call tty_port_install). They still have to
provide the link somehow though.
And this newly added function is exactly to serve that purpose.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
I forgot to document tty_port_register_device and tty_port_install
when they were added. Fix it now.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The termios and other changes mean the other protections needed on the driver
tty arrays should be adequate. Turn it all back on.
This contains pieces folded in from the fixes made to the original patches
| From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k)
| From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris)
| From: Jiri Kosina <jkosina@suze.cz> (lockdep)
| From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep)
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This will let us sort out a whole pile of tty related races. The
alternative would be to keep points and refcount the termios objects.
However
1. They are tiny anyway
2. Many devices don't use the stored copies
3. We can remove a pty special case
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
I sent GregKH this after the pre-requisites. He dropped the pre-requesites
for good reason and unfortunately then applied this patch. Without this
reverted you get random kernel memory corruption which will make bisecting
anything between it and the properly applied patches a complete sod.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The termios and other changes mean the other protections needed on the driver
tty arrays should be adequate. Turn it all back on.
This contains pieces folded in from the fixes made to the original patches
| From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k)
| From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris)
| From: Jiri Kosina <jkosina@suze.cz> (lockdep)
| From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep)
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This will automatically assign tty_port to tty_driver's port array for
later recall in tty_init_dev. This is intended to be called instead of
tty_register_device.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This will be used in tty_ops->install to set tty->port (and to call
tty_standard_install).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts the tty layer change to use per-tty locking, because it's
not correct yet, and fixing it will require some more deep surgery.
The main revert is d29f3ef39b ("tty_lock: Localise the lock"), but
there are several smaller commits that built upon it, they also get
reverted here. The list of reverted commits is:
fde86d3108 - tty: add lockdep annotations
8f6576ad47 - tty: fix ldisc lock inversion trace
d3ca8b64b9 - pty: Fix lock inversion
b1d679afd7 - tty: drop the pty lock during hangup
abcefe5fc3 - tty/amiserial: Add missing argument for tty_unlock()
fd11b42e35 - cris: fix missing tty arg in wait_event_interruptible_tty call
d29f3ef39b - tty_lock: Localise the lock
The revert had a trivial conflict in the 68360serial.c staging driver
that got removed in the meantime.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In each remaining case the tty_lock is associated with a specific tty. This
means we can now lock on a per tty basis. We do need tty_lock_pair() for
the pty case. Uglier but still a step in the right direction.
[fixed up calls in 3 missing drivers - gregkh]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 74c2107759 (serial: Use block_til_ready helper) and its fixup
3f582b8c11 (serial: fix termios settings in open) introduced a
regression on UV systems. The serial eventually freezes while being
used. It's completely unpredictable and sometimes needs a heap of
traffic to happen first.
To reproduce this, yast installation was used as it turned out to be
pretty reliable in reproducing. Especially during installation process
where one doesn't have an SSH daemon running. And no monitor as the HW
is completely headless. So this was fun to find. Given the machine
doesn't boot on vanilla before 2.6.36 final. (And the commits above
are older.)
Unless there is some bad race in the code, the hardware seems to be
pretty broken. Otherwise pure MSR read should not cause such a bug,
or?
So to prevent the bug, revert to the old behavior. I.e. read modem
status only if we really have to -- for non-CLOCAL set serials.
Non-CLOCAL works on this hardware OK, I tried. See? I don't.
And document that shit.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: stable <stable@vger.kernel.org>
References: https://lkml.org/lkml/2011/12/6/573
References: https://bugzilla.novell.com/show_bug.cgi?id=718518
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Let's use the newly added helper to avoid stalls in drivers which are
already ported to tty_port helpers.
We have to ensure here, that there is no user of tty_port_close_start
and tty_port_close which holds port->mutex (or other) lock over them.
And sure, there is none.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The tty code should be in its own subdirectory and not in the char
driver with all of the cruft that is currently there.
Based on work done by Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
