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661f7fda21
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>
103 lines
3.3 KiB
C
103 lines
3.3 KiB
C
/*
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* slip.h Define the SLIP device driver interface and constants.
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*
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* NOTE: THIS FILE WILL BE MOVED TO THE LINUX INCLUDE DIRECTORY
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* AS SOON AS POSSIBLE!
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*
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* Version: @(#)slip.h 1.2.0 03/28/93
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*
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* Fixes:
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* Alan Cox : Added slip mtu field.
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* Matt Dillon : Printable slip (borrowed from net2e)
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* Alan Cox : Added SL_SLIP_LOTS
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* Dmitry Gorodchanin : A lot of changes in the 'struct slip'
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* Dmitry Gorodchanin : Added CSLIP statistics.
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* Stanislav Voronyi : Make line checking as created by
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* Igor Chechik, RELCOM Corp.
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* Craig Schlenter : Fixed #define bug that caused
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* CSLIP telnets to hang in 1.3.61-6
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*
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* Author: Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
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*/
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#ifndef _LINUX_SLIP_H
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#define _LINUX_SLIP_H
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#if defined(CONFIG_INET) && defined(CONFIG_SLIP_COMPRESSED)
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# define SL_INCLUDE_CSLIP
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#endif
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#ifdef SL_INCLUDE_CSLIP
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# define SL_MODE_DEFAULT SL_MODE_ADAPTIVE
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#else
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# define SL_MODE_DEFAULT SL_MODE_SLIP
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#endif
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/* SLIP configuration. */
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#define SL_NRUNIT 256 /* MAX number of SLIP channels;
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This can be overridden with
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insmod -oslip_maxdev=nnn */
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#define SL_MTU 296 /* 296; I am used to 600- FvK */
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/* SLIP protocol characters. */
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#define END 0300 /* indicates end of frame */
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#define ESC 0333 /* indicates byte stuffing */
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#define ESC_END 0334 /* ESC ESC_END means END 'data' */
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#define ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */
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struct slip {
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int magic;
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/* Various fields. */
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struct tty_struct *tty; /* ptr to TTY structure */
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struct net_device *dev; /* easy for intr handling */
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spinlock_t lock;
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struct work_struct tx_work; /* Flushes transmit buffer */
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#ifdef SL_INCLUDE_CSLIP
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struct slcompress *slcomp; /* for header compression */
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unsigned char *cbuff; /* compression buffer */
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#endif
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/* These are pointers to the malloc()ed frame buffers. */
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unsigned char *rbuff; /* receiver buffer */
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int rcount; /* received chars counter */
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unsigned char *xbuff; /* transmitter buffer */
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unsigned char *xhead; /* pointer to next byte to XMIT */
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int xleft; /* bytes left in XMIT queue */
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int mtu; /* Our mtu (to spot changes!) */
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int buffsize; /* Max buffers sizes */
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#ifdef CONFIG_SLIP_MODE_SLIP6
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int xdata, xbits; /* 6 bit slip controls */
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#endif
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unsigned long flags; /* Flag values/ mode etc */
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#define SLF_INUSE 0 /* Channel in use */
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#define SLF_ESCAPE 1 /* ESC received */
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#define SLF_ERROR 2 /* Parity, etc. error */
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#define SLF_KEEPTEST 3 /* Keepalive test flag */
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#define SLF_OUTWAIT 4 /* is outpacket was flag */
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unsigned char mode; /* SLIP mode */
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unsigned char leased;
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pid_t pid;
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#define SL_MODE_SLIP 0
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#define SL_MODE_CSLIP 1
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#define SL_MODE_SLIP6 2 /* Matt Dillon's printable slip */
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#define SL_MODE_CSLIP6 (SL_MODE_SLIP6|SL_MODE_CSLIP)
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#define SL_MODE_AX25 4
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#define SL_MODE_ADAPTIVE 8
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#ifdef CONFIG_SLIP_SMART
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unsigned char outfill; /* # of sec between outfill packet */
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unsigned char keepalive; /* keepalive seconds */
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struct timer_list outfill_timer;
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struct timer_list keepalive_timer;
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#endif
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};
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#define SLIP_MAGIC 0x5302
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#endif /* _LINUX_SLIP.H */
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