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Message-ID: <20120524155121.20241.68413.stgit@bob.linux.org.uk> Date: Thu, 24 May 2012 16:51:31 +0100 From: Alan Cox <alan@...rguk.ukuu.org.uk> To: linux-kernel@...r.kernel.org Subject: [PATCH] tty: fix ldisc lock inversion trace From: Alan Cox <alan@...ux.intel.com> This is caused by tty_release using tty_lock_pair to lock both sides of the pty/tty pair, and then tty_ldisc_release dropping and relocking one side only. We can drop both fine, so drop both to avoid any lock ordering concerns. Signed-off-by: Alan Cox <alan@...ux.intel.com> --- drivers/tty/tty_ldisc.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 173a900..833e851 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -912,10 +912,13 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) * race with the set_ldisc code path. */ - tty_unlock(tty); + /* We don't give a monkeys' about the o_tty lock here but we + must do both to avoid lock inversions against another single + locking case */ + tty_unlock_pair(tty, o_tty); tty_ldisc_halt(tty); tty_ldisc_flush_works(tty); - tty_lock(tty); + tty_lock_pair(tty, o_tty); mutex_lock(&tty->ldisc_mutex); /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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