[PATCH v2 0/9] 3.8-rc regression with pps-ldisc due to 70ece7a731

From: George Spelvin
Date: Tue Feb 12 2013 - 09:54:46 EST

The standard N_TTY line discipline used to not use the tty->disc_data
field, so N_PPS felt free to use it. That has now changed, requiring
that N_PPS use a different method to find its private data.

(In the current, buggy, state, N_PPS follows a wild pointer and explodes
in an interrupt hander as soon as a pulse actually arrives.)

Compared to v1, this has been rearranges to the first three patches are
the minimial bugfixes:

* 1/9 "Add pps_lookup_dev() function"
This adds the infrastructure necessary to bypass disc_data use.

* 2/9 "Use pps_lookup_dev to reduce ldisc coupling"
This actually fixes the bug.

* 3/9 "Fix a use-after free bug when unregistering a source."
This is actually an old bug, present before 3.7. I'd like to solicit
feedback from folks who know device drivers better to ask if I did
things right. I'd also appreciate a look at patch 8/9 which is a more
aggressive cleanup of the same bug.

The remaining ones are various cleanups enabled or inspired by the

* 4/9 "Don't crash the machine when exiting will do"
This downgrades some BUG() checks do future bugs will be less deadly.
* 5/9 "Move timestamp read into PPS code proper"
This changes the internal kernel DCD change interface to capture the
timestamp inside the called function, cleaning up the generic tty code.
* 6/9 "Additional cleanups in uart_handle_dcd_change"
Just a slight code reorganization to shrink the source.
* 7/9 "Remove ancient hardpps()"
Eliminate dead code.
* 8/9 "Use a single cdev"
This is a more ambitious overhaul of the cdev business that patch
#3 fixes.
* 9/9 "use test_and_clear_bit in tty_ldisc_close"
Just a two-liner I noticed while working on the above.

George Spelvin (8):
pps: Add pps_lookup_dev() function
pps: Use pps_lookup_dev to reduce ldisc coupling
pps: Fix a use-after free bug when unregistering a source.
pps: Additional cleanups in uart_handle_dcd_change
pps: Use a single cdev
tty/tty_ldisc.c: use test_and_clear_bit in tty_ldisc_close

Peter Hurley (1):
pps: Move timestamp read into PPS code proper
pps: Don't crash the machine when exiting will do
tty: Remove ancient hardpps()

drivers/pps/clients/pps-ldisc.c | 30 +++++++----
drivers/pps/pps.c | 103 +++++++++++++++++++++++++-----------
drivers/staging/speakup/selection.c | 1 +
drivers/tty/amiserial.c | 5 --
drivers/tty/n_tty.c | 3 +-
drivers/tty/serial/serial_core.c | 24 +++------
drivers/tty/tty_buffer.c | 1 +
drivers/tty/tty_ldisc.c | 3 +-
include/linux/pps_kernel.h | 18 +++++--
include/linux/serial_core.h | 1 -
include/linux/tty_ldisc.h | 11 ++--
11 files changed, 122 insertions(+), 78 deletions(-)


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