Messages in this thread | | | Date | Mon, 16 Jun 2014 19:55:04 +0200 | From | Oliver Hartkopp <> | Subject | Re: [PATCH 1/2] slip: Fix deadlock in write_wakeup |
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Hello Tyler,
On 16.06.2014 04:23, Tyler Hall wrote: > Use schedule_work() to avoid potentially taking the spinlock in > interrupt context. > (..)
> > To deal with these issues, don't grab the lock in the wakeup function by > deferring the writeout to a workqueue. Also hold the lock during close > when de-assigning the tty pointer to safely disarm the worker and > timers. > > This bug is easily reproducible on the first transmit when slip is > used with the standard 8250 serial driver. >
looks reasonable. Thanks for your patch! Indeed I can't remember ever using the slcan driver with a real serial controller hardware with irq line but only via serial-to-USB adapters :-) Due to the recent fixes from Andre and Alexander these two drivers got in motion again ...
@Andre/Alexander: Can you please check if slcan still works in your setup. I don't have that hardware with me. I only was able to compile it successfully.
Just for the records: These two patches would be candidates for stable 3.12+
Thanks, Oliver
> [<c0410b7c>] (spin_bug+0x0/0x38) from [<c006109c>] (do_raw_spin_lock+0x60/0x1d0) > r5:eab27000 r4:ec02754c > [<c006103c>] (do_raw_spin_lock+0x0/0x1d0) from [<c04185c0>] (_raw_spin_lock+0x28/0x2c) > r10:0000001f r9:eabb814c r8:eabb8140 r7:40070193 r6:ec02754c r5:eab27000 > r4:ec02754c r3:00000000 > [<c0418598>] (_raw_spin_lock+0x0/0x2c) from [<bf3a0220>] (slip_write_wakeup+0x50/0xe0 [slip]) > r4:ec027540 r3:00000003 > [<bf3a01d0>] (slip_write_wakeup+0x0/0xe0 [slip]) from [<c026e420>] (tty_wakeup+0x48/0x68) > r6:00000000 r5:ea80c480 r4:eab27000 r3:bf3a01d0 > [<c026e3d8>] (tty_wakeup+0x0/0x68) from [<c028a8ec>] (uart_write_wakeup+0x2c/0x30) > r5:ed68ea90 r4:c06790d8 > [<c028a8c0>] (uart_write_wakeup+0x0/0x30) from [<c028dc44>] (serial8250_tx_chars+0x114/0x170) > [<c028db30>] (serial8250_tx_chars+0x0/0x170) from [<c028dffc>] (serial8250_handle_irq+0xa0/0xbc) > r6:000000c2 r5:00000060 r4:c06790d8 r3:00000000 > [<c028df5c>] (serial8250_handle_irq+0x0/0xbc) from [<c02933a4>] (dw8250_handle_irq+0x38/0x64) > r7:00000000 r6:edd2f390 r5:000000c2 r4:c06790d8 > [<c029336c>] (dw8250_handle_irq+0x0/0x64) from [<c028d2f4>] (serial8250_interrupt+0x44/0xc4) > r6:00000000 r5:00000000 r4:c06791c4 r3:c029336c > [<c028d2b0>] (serial8250_interrupt+0x0/0xc4) from [<c0067fe4>] (handle_irq_event_percpu+0xb4/0x2b0) > r10:c06790d8 r9:eab27000 r8:00000000 r7:00000000 r6:0000001f r5:edd52980 > r4:ec53b6c0 r3:c028d2b0 > [<c0067f30>] (handle_irq_event_percpu+0x0/0x2b0) from [<c006822c>] (handle_irq_event+0x4c/0x6c) > r10:c06790d8 r9:eab27000 r8:c0673ae0 r7:c05c2020 r6:ec53b6c0 r5:edd529d4 > r4:edd52980 > [<c00681e0>] (handle_irq_event+0x0/0x6c) from [<c006b140>] (handle_level_irq+0xe8/0x100) > r6:00000000 r5:edd529d4 r4:edd52980 r3:00022000 > [<c006b058>] (handle_level_irq+0x0/0x100) from [<c00676f8>] (generic_handle_irq+0x30/0x40) > r5:0000001f r4:0000001f > [<c00676c8>] (generic_handle_irq+0x0/0x40) from [<c000f57c>] (handle_IRQ+0xd0/0x13c) > r4:ea997b18 r3:000000e0 > [<c000f4ac>] (handle_IRQ+0x0/0x13c) from [<c00086c4>] (armada_370_xp_handle_irq+0x4c/0x118) > r8:000003ff r7:ea997b18 r6:ffffffff r5:60070013 r4:c0674dc0 > [<c0008678>] (armada_370_xp_handle_irq+0x0/0x118) from [<c0013840>] (__irq_svc+0x40/0x70) > Exception stack(0xea997b18 to 0xea997b60) > 7b00: 00000001 20070013 > 7b20: 00000000 0000000b 20070013 eab27000 20070013 00000000 ed10103e eab27000 > 7b40: c06790d8 ea997b74 ea997b60 ea997b60 c04186c0 c04186c8 60070013 ffffffff > r9:eab27000 r8:ed10103e r7:ea997b4c r6:ffffffff r5:60070013 r4:c04186c8 > [<c04186a4>] (_raw_spin_unlock_irqrestore+0x0/0x54) from [<c0288fc0>] (uart_start+0x40/0x44) > r4:c06790d8 r3:c028ddd8 > [<c0288f80>] (uart_start+0x0/0x44) from [<c028982c>] (uart_write+0xe4/0xf4) > r6:0000003e r5:00000000 r4:ed68ea90 r3:0000003e > [<c0289748>] (uart_write+0x0/0xf4) from [<bf3a0d20>] (sl_xmit+0x1c4/0x228 [slip]) > r10:ed388e60 r9:0000003c r8:ffffffdd r7:0000003e r6:ec02754c r5:ea717eb8 > r4:ec027000 > [<bf3a0b5c>] (sl_xmit+0x0/0x228 [slip]) from [<c0368d74>] (dev_hard_start_xmit+0x39c/0x6d0) > r8:eaf163c0 r7:ec027000 r6:ea717eb8 r5:00000000 r4:00000000 > > Signed-off-by: Tyler Hall <tylerwhall@gmail.com> > Cc: Oliver Hartkopp <socketcan@hartkopp.net> > Cc: Andre Naujoks <nautsch2@gmail.com> > Cc: David S. Miller <davem@davemloft.net> > Cc: linux-kernel@vger.kernel.org > --- > drivers/net/slip/slip.c | 36 ++++++++++++++++++++++++++---------- > drivers/net/slip/slip.h | 1 + > 2 files changed, 27 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c > index ad4a94e..8752644 100644 > --- a/drivers/net/slip/slip.c > +++ b/drivers/net/slip/slip.c > @@ -83,6 +83,7 @@ > #include <linux/delay.h> > #include <linux/init.h> > #include <linux/slab.h> > +#include <linux/workqueue.h> > #include "slip.h" > #ifdef CONFIG_INET > #include <linux/ip.h> > @@ -416,36 +417,46 @@ static void sl_encaps(struct slip *sl, unsigned char *icp, int len) > #endif > } > > -/* > - * Called by the driver when there's room for more data. If we have > - * more packets to send, we send them here. > - */ > -static void slip_write_wakeup(struct tty_struct *tty) > +/* Write out any remaining transmit buffer. Scheduled when tty is writable */ > +static void slip_transmit(struct work_struct *work) > { > + struct slip *sl = container_of(work, struct slip, tx_work); > int actual; > - struct slip *sl = tty->disc_data; > > + spin_lock_bh(&sl->lock); > /* First make sure we're connected. */ > - if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) > + if (!sl->tty || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) { > + spin_unlock_bh(&sl->lock); > return; > + } > > - spin_lock_bh(&sl->lock); > if (sl->xleft <= 0) { > /* Now serial buffer is almost free & we can start > * transmission of another packet */ > sl->dev->stats.tx_packets++; > - clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); > + clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags); > spin_unlock_bh(&sl->lock); > sl_unlock(sl); > return; > } > > - actual = tty->ops->write(tty, sl->xhead, sl->xleft); > + actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft); > sl->xleft -= actual; > sl->xhead += actual; > spin_unlock_bh(&sl->lock); > } > > +/* > + * Called by the driver when there's room for more data. > + * Schedule the transmit. > + */ > +static void slip_write_wakeup(struct tty_struct *tty) > +{ > + struct slip *sl = tty->disc_data; > + > + schedule_work(&sl->tx_work); > +} > + > static void sl_tx_timeout(struct net_device *dev) > { > struct slip *sl = netdev_priv(dev); > @@ -749,6 +760,7 @@ static struct slip *sl_alloc(dev_t line) > sl->magic = SLIP_MAGIC; > sl->dev = dev; > spin_lock_init(&sl->lock); > + INIT_WORK(&sl->tx_work, slip_transmit); > sl->mode = SL_MODE_DEFAULT; > #ifdef CONFIG_SLIP_SMART > /* initialize timer_list struct */ > @@ -872,8 +884,12 @@ static void slip_close(struct tty_struct *tty) > if (!sl || sl->magic != SLIP_MAGIC || sl->tty != tty) > return; > > + spin_lock_bh(&sl->lock); > tty->disc_data = NULL; > sl->tty = NULL; > + spin_unlock_bh(&sl->lock); > + > + flush_work(&sl->tx_work); > > /* VSV = very important to remove timers */ > #ifdef CONFIG_SLIP_SMART > diff --git a/drivers/net/slip/slip.h b/drivers/net/slip/slip.h > index 67673cf..cf32aad 100644 > --- a/drivers/net/slip/slip.h > +++ b/drivers/net/slip/slip.h > @@ -53,6 +53,7 @@ struct slip { > struct tty_struct *tty; /* ptr to TTY structure */ > struct net_device *dev; /* easy for intr handling */ > spinlock_t lock; > + struct work_struct tx_work; /* Flushes transmit buffer */ > > #ifdef SL_INCLUDE_CSLIP > struct slcompress *slcomp; /* for header compression */ >
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