linux-toradex.git/drivers/tty/n_hdlc.c, branch v3.4.4

Remove all #inclusions of asm/system.h

2012-03-28T17:30:03+00:00

Remove all #inclusions of asm/system.h preparatory to splitting and killing
it.  Performed with the following command:

perl -p -i -e 's!^#\s*include\s*.*\n!!' `grep -Irl '^#\s*include\s*' *`

Signed-off-by: David Howells

tty: n_hdlc not atomic use tty->flags.

2011-11-30T12:30:49+00:00

N_HDLC can spoil tty->flags because use not atomic operations on tty->flags.
I use n_hdlc line discipline and it happens.

Signed-off-by: Ilya Zykov 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

Revert "tty: make receive_buf() return the amout of bytes received"

2011-06-03T21:33:24+00:00

This reverts commit b1c43f82c5aa265442f82dba31ce985ebb7aa71c.

It was broken in so many ways, and results in random odd pty issues.

It re-introduced the buggy schedule_work() in flush_to_ldisc() that can
cause endless work-loops (see commit a5660b41af6a: "tty: fix endless
work loop when the buffer fills up").

It also used an "unsigned int" return value fo the ->receive_buf()
function, but then made multiple functions return a negative error code,
and didn't actually check for the error in the caller.

And it didn't actually work at all.  BenH bisected down odd tty behavior
to it:
  "It looks like the patch is causing some major malfunctions of the X
   server for me, possibly related to PTYs.  For example, cat'ing a
   large file in a gnome terminal hangs the kernel for -minutes- in a
   loop of what looks like flush_to_ldisc/workqueue code, (some ftrace
   data in the quoted bits further down).

   ...

   Some more data: It -looks- like what happens is that the
   flush_to_ldisc work queue entry constantly re-queues itself (because
   the PTY is full ?) and the workqueue thread will basically loop
   forver calling it without ever scheduling, thus starving the consumer
   process that could have emptied the PTY."

which is pretty much exactly the problem we fixed in a5660b41af6a.

Milton Miller pointed out the 'unsigned int' issue.

Reported-by: Benjamin Herrenschmidt 
Reported-by: Milton Miller 
Cc: Stefan Bigler 
Cc: Toby Gray 
Cc: Felipe Balbi 
Cc: Greg Kroah-Hartman 
Cc: Alan Cox 
Signed-off-by: Linus Torvalds

tty: make receive_buf() return the amout of bytes received

2011-04-23T00:31:53+00:00

it makes it simpler to keep track of the amount of
bytes received and simplifies how flush_to_ldisc counts
the remaining bytes. It also fixes a bug of lost bytes
on n_tty when flushing too many bytes via the USB
serial gadget driver.

Tested-by: Stefan Bigler 
Tested-by: Toby Gray 
Signed-off-by: Felipe Balbi 
Signed-off-by: Greg Kroah-Hartman

drivers: remove extraneous includes of smp_lock.h

2011-03-01T23:02:40+00:00

These were missed the last time I cleaned this up
globally, because of code moving around or new code
getting merged.

Signed-off-by: Arnd Bergmann

n_hdlc: fix read and write locking

2011-01-23T03:15:01+00:00

Fix locking in read and write code of n_hdlc line discipline.

2.6.36 replaced lock_kernel() with tty_lock().  The tty mutex is not
dropped automatically when the thread sleeps like the BKL.  This results
in a blocked read or write holding the tty mutex and stalling operations
by other devices that use the tty mutex.

A review of n_hdlc read and write code shows:
1. neither BKL or tty mutex are required for correct operation
2. read can block while read data is available if data is posted
   between availability check and call to interruptible_sleep_on()
3. write does not set process state to TASK_INTERRUPTIBLE
   on each pass through the processing loop which can cause
   unneeded scheduling of the thread

The unnecessary tty mutex references have been removed.

Read changed to use same code as n_tty read
for completing reads and blocking.

Write corrected to set process state to TASK_INTERRUPTIBLE on each pass
through processing loop.

Signed-off-by: Paul Fulghum 
Acked-by: Arnd Bergmann 
Cc: Alan Cox 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

TTY: create drivers/tty and move the tty core files there

2010-11-05T15:10:33+00:00

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 

Acked-by: Arnd Bergmann 
Cc: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman