linux-toradex.git/drivers/tty/tty_port.c, branch v4.3.3

tty: Deletion of unnecessary checks before two function calls

2014-11-27T03:35:49+00:00

The functions put_device() and tty_kref_put() test whether their argument
is NULL and then return immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring 
Signed-off-by: Greg Kroah-Hartman

tty: Flush tty buffers after hardware shutdown

2014-11-06T22:57:27+00:00

The line discipline buffer and the tty buffers must be flushed again
after hardware shutdown; otherwise, a brief window exists between the
ldisc flush in tty_port_close_start() and the subsequent
tty_port_shutdown(), during which more data could be received into the
tty buffers. A racing open might then be able to receive data from the
previous session.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Move tty hung up check from port->lock critical section

2014-11-06T22:57:27+00:00

The port->lock does not protect the filp->f_op field; move
the tty_hung_up_p() test outside the port->lock critical section
in tty_port_close_start().

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Remove tty_hung_up_p() tests from tty drivers' open()

2014-07-10T23:06:49+00:00

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 
CC: Samuel Ortiz 
CC: "David S. Miller" 
Signed-off-by: Peter Hurley 
Acked-by: Jesper Nilsson 
Signed-off-by: Greg Kroah-Hartman

tty: Move tty->closing from port lock critical section

2014-07-10T23:06:48+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: Document locking for tty_port_hangup()

2014-07-10T23:05:19+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: Document locking for tty_port_block_til_ready()

2014-07-10T23:05:19+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: Document locking for tty_port_open()

2014-07-10T23:05:19+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: Document locking for tty_port_close{,start,end}()

2014-07-10T23:05:19+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: delete non-required instances of include

2014-01-08T01:05:21+00:00

None of these files are actually using any __init type directives
and hence don't need to include .  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 
Signed-off-by: Greg Kroah-Hartman