diff options
author | Tyler Hall <tylerwhall@gmail.com> | 2014-06-15 22:23:16 -0400 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-06-16 21:29:12 -0700 |
commit | 661f7fda21b15ec52f57fcd397c03370acc28688 (patch) | |
tree | e23b6e136614f9e08dc2aa663345719b93065aed /drivers | |
parent | f00e2b0ac3ae25a37c04a113ed03bf249fad15d8 (diff) | |
download | linux-661f7fda21b15ec52f57fcd397c03370acc28688.tar.bz2 |
slip: Fix deadlock in write_wakeup
Use schedule_work() to avoid potentially taking the spinlock in
interrupt context.
Commit cc9fa74e2a ("slip/slcan: added locking in wakeup function") added
necessary locking to the wakeup function and 367525c8c2/ddcde142be ("can:
slcan: Fix spinlock variant") converted it to spin_lock_bh() because the lock
is also taken in timers.
Disabling softirqs is not sufficient, however, as tty drivers may call
write_wakeup from interrupt context. This driver calls tty->ops->write() with
its spinlock held, which may immediately cause an interrupt on the same CPU and
subsequent spin_bug().
Simply converting to spin_lock_irq/irqsave() prevents this deadlock, but
causes lockdep to point out a possible circular locking dependency
between these locks:
(&(&sl->lock)->rlock){-.....}, at: slip_write_wakeup
(&port_lock_key){-.....}, at: serial8250_handle_irq.part.13
The slip transmit is holding the slip spinlock when calling the tty write.
This grabs the port lock. On an interrupt, the handler grabs the port
lock and calls write_wakeup which grabs the slip lock. This could be a
problem if a serial interrupt occurs on another CPU during the slip
transmit.
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.
[<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
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/net/slip/slip.c | 36 | ||||
-rw-r--r-- | 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 ad4a94e9ff57..87526443841f 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 67673cf1266b..cf32aadf508f 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 */ |