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Jiri Slaby authored
commit e9b736d8 upstream. The class of 4 n_hdls buf locks is the same because a single function n_hdlc_buf_list_init is used to init all the locks. But since flush_tx_queue takes n_hdlc->tx_buf_list.spinlock and then calls n_hdlc_buf_put which takes n_hdlc->tx_free_buf_list.spinlock, lockdep emits a warning: ============================================= [ INFO: possible recursive locking detected ] 4.3.0-25.g91e30a7-default #1 Not tainted --------------------------------------------- a.out/1248 is trying to acquire lock: (&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fd020>] n_hdlc_buf_put+0x20/0x60 [n_hdlc] but task is already holding lock: (&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fdc07>] n_hdlc_tty_ioctl+0x127/0x1d0 [n_hdlc] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&list->spinlock)->rlock); lock(&(&list->spinlock)->rlock); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by a.out/1248: #0: (&tty->ldisc_sem){++++++}, at: [<ffffffff814c9eb0>] tty_ldisc_ref_wait+0x20/0x50 #1: (&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fdc07>] n_hdlc_tty_ioctl+0x127/0x1d0 [n_hdlc] ... Call Trace: ... [<ffffffff81738fd0>] _raw_spin_lock_irqsave+0x50/0x70 [<ffffffffa01fd020>] n_hdlc_buf_put+0x20/0x60 [n_hdlc] [<ffffffffa01fdc24>] n_hdlc_tty_ioctl+0x144/0x1d0 [n_hdlc] [<ffffffff814c25c1>] tty_ioctl+0x3f1/0xe40 ... Fix it by initializing the spin_locks separately. This removes also reduntand memset of a freshly kzallocated space. Signed-off-by:
Jiri Slaby <jslaby@suse.cz> Reported-by:
Dmitry Vyukov <dvyukov@google.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:
Ben Hutchings <ben@decadent.org.uk>
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