| Message ID | 20140320182528.GE3959@saruman.home |
|---|---|
| State | New |
| Headers | show |
On Thu, Mar 20, 2014 at 01:25:28PM -0500, Felipe Balbi wrote: > On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote: > > On 03/20/2014 02:11 PM, Felipe Balbi wrote: > > >On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote: > > >>[ +cc Huang Shijie ] > > >> > > >>On 03/20/2014 01:16 PM, Felipe Balbi wrote: > > >>>On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote: > > >>>>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote: > > >>>>>Hi, > > >>>>> > > >>>>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already > > >>>>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls > > >>>>>tty->ops->write() to actually send the characters, but that call will > > >>>>>try to acquire the same port lock again. > > >>>>> > > >>>>>Looking at other line disciplines that looks like a bug in hci_ldisc.c. > > >>>>>Am I correct to assume that ->write_wakeup() is supposed to *just* > > >>>>>wakeup the bottom half so we handle ->write() in another context ? > > >>>>> > > >>>>>Is it legal to call tty->ops->write() from within ->write_wakeup() ? > > >>>> > > >>>>It isn't because you might send all the bytes and go > > >>>> > > >>>> write > > >>>> write_wakeup > > >>>> write > > >>>> write wakeup > > >>>> ... > > >>>> > > >>>>and recurse > > >>> > > >>>cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do > > >>>you want this to be sorted out ? > > >> > > >>hci_uart_tx_wakeup() should perform the I/O as work. > > >>FWIW, this was reported by Huang Shijie back on Dec 6. > > >> > > >>I'd fix it but I have no way to test it. > > > > > >here's a build-tested only patch which is waiting for testing from other > > >colleagues who've got a platform to reproduce the problem: > > > > Where's the cancel_work_sync() on teardown? > > here, as a patch too this time: > > From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001 > From: Felipe Balbi <balbi@ti.com> > Date: Thu, 20 Mar 2014 13:20:10 -0500 > Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition > > LDISCs shouldn't call tty->ops->write() from within > ->write_wakeup(). > > ->write_wakeup() is called with port lock taken and > IRQs disabled, tty->ops->write() will try to acquire > the same port lock and we will deadlock. > > Signed-off-by: Felipe Balbi <balbi@ti.com> > --- > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++----- > drivers/bluetooth/hci_uart.h | 1 + > 2 files changed, 16 insertions(+), 5 deletions(-) > > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c > index 6e06f6f..ecdd765 100644 > --- a/drivers/bluetooth/hci_ldisc.c > +++ b/drivers/bluetooth/hci_ldisc.c > @@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) > > int hci_uart_tx_wakeup(struct hci_uart *hu) > { > - struct tty_struct *tty = hu->tty; > - struct hci_dev *hdev = hu->hdev; > - struct sk_buff *skb; > - > if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { > set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > return 0; > @@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu) > > BT_DBG(""); > > + schedule_work(&hu->write_work); > + > + return 0; > +} > + > +static void hci_uart_write_work(struct work_struct *work) > +{ > + struct hci_uart *hu = container_of(work, struct hci_uart, init_ready); > + struct tty_struct *tty = hu->tty; > + struct hci_dev *hdev = hu->hdev; > + struct sk_buff *skb; > + > restart: > clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > > @@ -153,7 +161,6 @@ restart: > goto restart; > > clear_bit(HCI_UART_SENDING, &hu->tx_state); > - return 0; > } > > static void hci_uart_init_work(struct work_struct *work) > @@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty) > tty->receive_room = 65536; > > INIT_WORK(&hu->init_ready, hci_uart_init_work); > + INIT_WORK(&hu->write_work, hci_uart_write_work); > > spin_lock_init(&hu->rx_lock); > > @@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty) > if (hdev) > hci_uart_close(hdev); > > + cancel_work_sync(&hy->write_work); forgot to commit, darn it
On 03/20/2014 02:25 PM, Felipe Balbi wrote: > On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote: >> On 03/20/2014 02:11 PM, Felipe Balbi wrote: >>> On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote: >>>> [ +cc Huang Shijie ] >>>> >>>> On 03/20/2014 01:16 PM, Felipe Balbi wrote: >>>>> On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote: >>>>>> On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote: >>>>>>> Hi, >>>>>>> >>>>>>> when 8250 driver calls uart_write_wakeup(), the tty port lock is already >>>>>>> taken. hci_ldisc.c's implementation of ->write_wakeup() calls >>>>>>> tty->ops->write() to actually send the characters, but that call will >>>>>>> try to acquire the same port lock again. >>>>>>> >>>>>>> Looking at other line disciplines that looks like a bug in hci_ldisc.c. >>>>>>> Am I correct to assume that ->write_wakeup() is supposed to *just* >>>>>>> wakeup the bottom half so we handle ->write() in another context ? >>>>>>> >>>>>>> Is it legal to call tty->ops->write() from within ->write_wakeup() ? >>>>>> >>>>>> It isn't because you might send all the bytes and go >>>>>> >>>>>> write >>>>>> write_wakeup >>>>>> write >>>>>> write wakeup >>>>>> ... >>>>>> >>>>>> and recurse >>>>> >>>>> cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do >>>>> you want this to be sorted out ? >>>> >>>> hci_uart_tx_wakeup() should perform the I/O as work. >>>> FWIW, this was reported by Huang Shijie back on Dec 6. >>>> >>>> I'd fix it but I have no way to test it. >>> >>> here's a build-tested only patch which is waiting for testing from other >>> colleagues who've got a platform to reproduce the problem: >> >> Where's the cancel_work_sync() on teardown? > > here, as a patch too this time: Thanks. Minor edits below but, strictly speaking, not necessary. Reviewed-by: Peter Hurley <peter@hurleysoftware.com> > From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001 > From: Felipe Balbi <balbi@ti.com> > Date: Thu, 20 Mar 2014 13:20:10 -0500 > Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition > > LDISCs shouldn't call tty->ops->write() from within > ->write_wakeup(). > > ->write_wakeup() is called with port lock taken and > IRQs disabled, tty->ops->write() will try to acquire > the same port lock and we will deadlock. > I know you found it independently but ? Reported-by: Huang Shijie <b32955@freescale.com> > Signed-off-by: Felipe Balbi <balbi@ti.com> > --- > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++----- > drivers/bluetooth/hci_uart.h | 1 + > 2 files changed, 16 insertions(+), 5 deletions(-) > > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c > index 6e06f6f..ecdd765 100644 > --- a/drivers/bluetooth/hci_ldisc.c > +++ b/drivers/bluetooth/hci_ldisc.c > @@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) > > int hci_uart_tx_wakeup(struct hci_uart *hu) > { > - struct tty_struct *tty = hu->tty; > - struct hci_dev *hdev = hu->hdev; > - struct sk_buff *skb; > - > if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { > set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > return 0; > @@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu) > > BT_DBG(""); > > + schedule_work(&hu->write_work); > + > + return 0; > +} > + > +static void hci_uart_write_work(struct work_struct *work) > +{ > + struct hci_uart *hu = container_of(work, struct hci_uart, init_ready); > + struct tty_struct *tty = hu->tty; > + struct hci_dev *hdev = hu->hdev; > + struct sk_buff *skb; > + + /* FIXME: if bad skb length or tty->ops->write() returns < 0 ??? */ > restart: > clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > > @@ -153,7 +161,6 @@ restart: > goto restart; > > clear_bit(HCI_UART_SENDING, &hu->tx_state); > - return 0; > } > > static void hci_uart_init_work(struct work_struct *work) > @@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty) > tty->receive_room = 65536; > > INIT_WORK(&hu->init_ready, hci_uart_init_work); > + INIT_WORK(&hu->write_work, hci_uart_write_work); > > spin_lock_init(&hu->rx_lock); > > @@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty) > if (hdev) > hci_uart_close(hdev); > > + cancel_work_sync(&hy->write_work); > + > if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) { > if (hdev) { > if (test_bit(HCI_UART_REGISTERED, &hu->flags)) > diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h > index fffa61f..12df101 100644 > --- a/drivers/bluetooth/hci_uart.h > +++ b/drivers/bluetooth/hci_uart.h > @@ -68,6 +68,7 @@ struct hci_uart { > unsigned long hdev_flags; > > struct work_struct init_ready; > + struct work_struct write_work; > > struct hci_uart_proto *proto; > void *priv; > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Hi, On Thu, Mar 20, 2014 at 03:16:35PM -0400, Peter Hurley wrote: > On 03/20/2014 02:25 PM, Felipe Balbi wrote: > >On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote: > >>On 03/20/2014 02:11 PM, Felipe Balbi wrote: > >>>On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote: > >>>>[ +cc Huang Shijie ] > >>>> > >>>>On 03/20/2014 01:16 PM, Felipe Balbi wrote: > >>>>>On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote: > >>>>>>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote: > >>>>>>>Hi, > >>>>>>> > >>>>>>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already > >>>>>>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls > >>>>>>>tty->ops->write() to actually send the characters, but that call will > >>>>>>>try to acquire the same port lock again. > >>>>>>> > >>>>>>>Looking at other line disciplines that looks like a bug in hci_ldisc.c. > >>>>>>>Am I correct to assume that ->write_wakeup() is supposed to *just* > >>>>>>>wakeup the bottom half so we handle ->write() in another context ? > >>>>>>> > >>>>>>>Is it legal to call tty->ops->write() from within ->write_wakeup() ? > >>>>>> > >>>>>>It isn't because you might send all the bytes and go > >>>>>> > >>>>>> write > >>>>>> write_wakeup > >>>>>> write > >>>>>> write wakeup > >>>>>> ... > >>>>>> > >>>>>>and recurse > >>>>> > >>>>>cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do > >>>>>you want this to be sorted out ? > >>>> > >>>>hci_uart_tx_wakeup() should perform the I/O as work. > >>>>FWIW, this was reported by Huang Shijie back on Dec 6. > >>>> > >>>>I'd fix it but I have no way to test it. > >>> > >>>here's a build-tested only patch which is waiting for testing from other > >>>colleagues who've got a platform to reproduce the problem: > >> > >>Where's the cancel_work_sync() on teardown? > > > >here, as a patch too this time: > > Thanks. Minor edits below but, strictly speaking, not necessary. > > Reviewed-by: Peter Hurley <peter@hurleysoftware.com> > > > > From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001 > >From: Felipe Balbi <balbi@ti.com> > >Date: Thu, 20 Mar 2014 13:20:10 -0500 > >Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition > > > >LDISCs shouldn't call tty->ops->write() from within > >->write_wakeup(). > > > >->write_wakeup() is called with port lock taken and > >IRQs disabled, tty->ops->write() will try to acquire > >the same port lock and we will deadlock. > > > > I know you found it independently but ? > > Reported-by: Huang Shijie <b32955@freescale.com> I will never add any *-by tags without seeing it in the mailing list. Now I can add it to the patch and send it as a real patch (git send-email it). > >Signed-off-by: Felipe Balbi <balbi@ti.com> > >--- > > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++----- > > drivers/bluetooth/hci_uart.h | 1 + > > 2 files changed, 16 insertions(+), 5 deletions(-) > > > >diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c > >index 6e06f6f..ecdd765 100644 > >--- a/drivers/bluetooth/hci_ldisc.c > >+++ b/drivers/bluetooth/hci_ldisc.c > >@@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) > > > > int hci_uart_tx_wakeup(struct hci_uart *hu) > > { > >- struct tty_struct *tty = hu->tty; > >- struct hci_dev *hdev = hu->hdev; > >- struct sk_buff *skb; > >- > > if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { > > set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > > return 0; > >@@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu) > > > > BT_DBG(""); > > > >+ schedule_work(&hu->write_work); > >+ > >+ return 0; > >+} > >+ > >+static void hci_uart_write_work(struct work_struct *work) > >+{ > >+ struct hci_uart *hu = container_of(work, struct hci_uart, init_ready); > >+ struct tty_struct *tty = hu->tty; > >+ struct hci_dev *hdev = hu->hdev; > >+ struct sk_buff *skb; > >+ > > + /* FIXME: if bad skb length or tty->ops->write() returns < 0 ??? */ > > > restart: > > clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); > > > >@@ -153,7 +161,6 @@ restart: > > goto restart; > > > > clear_bit(HCI_UART_SENDING, &hu->tx_state); > >- return 0; > > } > > > > static void hci_uart_init_work(struct work_struct *work) > >@@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty) > > tty->receive_room = 65536; > > > > INIT_WORK(&hu->init_ready, hci_uart_init_work); > >+ INIT_WORK(&hu->write_work, hci_uart_write_work); > > > > spin_lock_init(&hu->rx_lock); > > > >@@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty) > > if (hdev) > > hci_uart_close(hdev); > > > >+ cancel_work_sync(&hy->write_work); > >+ > > if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) { > > if (hdev) { > > if (test_bit(HCI_UART_REGISTERED, &hu->flags)) > >diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h > >index fffa61f..12df101 100644 > >--- a/drivers/bluetooth/hci_uart.h > >+++ b/drivers/bluetooth/hci_uart.h > >@@ -68,6 +68,7 @@ struct hci_uart { > > unsigned long hdev_flags; > > > > struct work_struct init_ready; > >+ struct work_struct write_work; > > > > struct hci_uart_proto *proto; > > void *priv; > > >
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index 6e06f6f..ecdd765 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) int hci_uart_tx_wakeup(struct hci_uart *hu) { - struct tty_struct *tty = hu->tty; - struct hci_dev *hdev = hu->hdev; - struct sk_buff *skb; - if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); return 0; @@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu) BT_DBG(""); + schedule_work(&hu->write_work); + + return 0; +} + +static void hci_uart_write_work(struct work_struct *work) +{ + struct hci_uart *hu = container_of(work, struct hci_uart, init_ready); + struct tty_struct *tty = hu->tty; + struct hci_dev *hdev = hu->hdev; + struct sk_buff *skb; + restart: clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); @@ -153,7 +161,6 @@ restart: goto restart; clear_bit(HCI_UART_SENDING, &hu->tx_state); - return 0; } static void hci_uart_init_work(struct work_struct *work) @@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty) tty->receive_room = 65536; INIT_WORK(&hu->init_ready, hci_uart_init_work); + INIT_WORK(&hu->write_work, hci_uart_write_work); spin_lock_init(&hu->rx_lock); @@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty) if (hdev) hci_uart_close(hdev); + cancel_work_sync(&hy->write_work); + if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) { if (hdev) { if (test_bit(HCI_UART_REGISTERED, &hu->flags)) diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h index fffa61f..12df101 100644 --- a/drivers/bluetooth/hci_uart.h +++ b/drivers/bluetooth/hci_uart.h @@ -68,6 +68,7 @@ struct hci_uart { unsigned long hdev_flags; struct work_struct init_ready; + struct work_struct write_work; struct hci_uart_proto *proto; void *priv;