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tty: fix BKL related leak and crash 

Enabling the BKL to be lockdep tracked uncovered the following
upstream kernel bug in the tty code, which caused a BKL
reference leak:

  ================================================
  [ BUG: lock held when returning to user space! ]
  ------------------------------------------------
  dmesg/3121 is leaving the kernel with locks still held!
  1 lock held by dmesg/3121:
   #0:  (kernel_mutex){--..}, at: [<c02f34d9>] opost+0x24/0x194

this might explain some of the atomicity warnings and crashes
that -tip tree testing has been experiencing since the BKL
was converted back to a spinlock.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ingo Molnar 2008-05-14 17:11:46 +02:00 committed by Linus Torvalds
parent 8568dae21e
commit 487ad7efbf
1 changed files with 10 additions and 3 deletions
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13
drivers/char/n_tty.c
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@ -282,16 +282,20 @@ static int opost(unsigned char c, struct tty_struct *tty)
if (O_ONLRET(tty))
tty->column = 0;
if (O_ONLCR(tty)) {
if (space < 2)
if (space < 2) {
unlock_kernel();
return -1;
}
tty_put_char(tty, '\r');
tty->column = 0;
}
tty->canon_column = tty->column;
break;
case '\r':
if (O_ONOCR(tty) && tty->column == 0)
if (O_ONOCR(tty) && tty->column == 0) {
unlock_kernel();
return 0;
}
if (O_OCRNL(tty)) {
c = '\n';
if (O_ONLRET(tty))
@ -303,10 +307,13 @@ static int opost(unsigned char c, struct tty_struct *tty)
case '\t':
spaces = 8 - (tty->column & 7);
if (O_TABDLY(tty) == XTABS) {
if (space < spaces)
if (space < spaces) {
unlock_kernel();
return -1;
}
tty->column += spaces;
tty->ops->write(tty, " ", spaces);
unlock_kernel();
return 0;
}
tty->column += spaces;