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authorAlan Cox <alan@linux.intel.com>2009-07-16 16:07:03 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-16 09:19:16 -0700
commit807708844979ba8c6d5717345a8608454992696d (patch)
tree97daa91a0ddd6ed6fe48a5967762523c4fe1f924 /drivers/char/n_tty.c
parent9237a81a1468d0aca1cc4e244bba2362d6f81b35 (diff)
downloadlinux-linaro-stable-807708844979ba8c6d5717345a8608454992696d.tar.gz
n_tty: Fix echo race
If a tty in N_TTY mode with echo enabled manages to get itself into a state where - echo characters are pending - FASYNC is enabled - tty_write_wakeup is called from either - a device write path (pty) - an IRQ (serial) then it either deadlocks or explodes taking a mutex in the IRQ path. On the serial side it is almost impossible to reproduce because you have to go from a full serial port to a near empty one with echo characters pending. The pty case happens to have become possible to trigger using emacs and ptys, the pty changes having created a scenario which shows up this bug. The code path is n_tty:process_echoes() (takes mutex) tty_io:tty_put_char() pty:pty_write (or serial paths) tty_wakeup (from pty_write or serial IRQ) n_tty_write_wakeup() process_echoes() *KABOOM* Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char/n_tty.c')
-rw-r--r--drivers/char/n_tty.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 94a5d5020abc..ff47907ff1bf 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1331,9 +1331,6 @@ handle_newline:
static void n_tty_write_wakeup(struct tty_struct *tty)
{
- /* Write out any echoed characters that are still pending */
- process_echoes(tty);
-
if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
}