diff options
| author | Jiri Slaby <jslaby@suse.cz> | 2015-11-26 21:28:26 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-02-07 10:27:46 +0300 |
| commit | e9b736d88af1a143530565929390cadf036dc799 (patch) | |
| tree | c81d977d29d09ad33e4f6255d0352c5662fecbf1 /drivers/tty/n_hdlc.c | |
| parent | b1209983d2c012be8d253ed118f9281ed9f46af6 (diff) | |
| download | linux-e9b736d88af1a143530565929390cadf036dc799.tar.xz | |
TTY: n_hdlc, fix lockdep false positive
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>
Diffstat (limited to 'drivers/tty/n_hdlc.c')
| -rw-r--r-- | drivers/tty/n_hdlc.c | 19 |
1 files changed, 4 insertions, 15 deletions
diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c index bbc4ce66c2c1..bcaba17688f6 100644 --- a/drivers/tty/n_hdlc.c +++ b/drivers/tty/n_hdlc.c @@ -159,7 +159,6 @@ struct n_hdlc { /* * HDLC buffer list manipulation functions */ -static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list); static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, struct n_hdlc_buf *buf); static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); @@ -853,10 +852,10 @@ static struct n_hdlc *n_hdlc_alloc(void) if (!n_hdlc) return NULL; - n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list); - n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list); - n_hdlc_buf_list_init(&n_hdlc->rx_buf_list); - n_hdlc_buf_list_init(&n_hdlc->tx_buf_list); + spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); + spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); + spin_lock_init(&n_hdlc->rx_buf_list.spinlock); + spin_lock_init(&n_hdlc->tx_buf_list.spinlock); /* allocate free rx buffer list */ for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) { @@ -885,16 +884,6 @@ static struct n_hdlc *n_hdlc_alloc(void) } /* end of n_hdlc_alloc() */ /** - * n_hdlc_buf_list_init - initialize specified HDLC buffer list - * @list - pointer to buffer list - */ -static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list) -{ - memset(list, 0, sizeof(*list)); - spin_lock_init(&list->spinlock); -} /* end of n_hdlc_buf_list_init() */ - -/** * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list * @list - pointer to buffer list * @buf - pointer to buffer |