tty: fix BKL related leak and crash (487ad7ef) · Commits · 戴 / test

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>

drivers/char/n_tty.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -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;

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