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| author | Peter Hurley <peter@hurleysoftware.com> | 2013-03-11 21:44:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-03-19 00:48:42 +0100 |
| commit | 16759f6cd8c590fa23cb2956fdf32fe23a67e482 (patch) | |
| tree | cfd1c8eb346d6cae8bf82cc2211b21f79b449671 /drivers/spi/spi-ep93xx.c | |
| parent | tty: Separate release semantics of ldisc reference (diff) | |
| download | linux-16759f6cd8c590fa23cb2956fdf32fe23a67e482.tar.xz linux-16759f6cd8c590fa23cb2956fdf32fe23a67e482.zip | |
tty: Document unsafe ldisc reference acquire
Merge get_ldisc() into its only call site.
Note how, after merging, the unsafe acquire of an ldisc reference
is obvious.
CPU 0 in tty_ldisc_try() | CPU 1 in tty_ldisc_halt()
|
test_bit(TTY_LDISC, &tty_flags) |
if (true) | clear_bit(TTY_LDISC, &tty_flags)
tty->ldisc != 0? | atomic_read(&tty->ldisc->users)
if (true) | ret_val == 1?
atomic_inc(&tty->ldisc->users) | if (false)
| wait
|
<goes on assuming safe ldisc use> | <doesn't wait - proceeds w/ close>
|
The spin lock in tty_ldisc_try() does nothing wrt synchronizing
the ldisc halt since it's not acquired as part of halting.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to '')
0 files changed, 0 insertions, 0 deletions