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Subject[PATCH 1/1] Char: isicom, fix card locking
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Date
Could you test this one and turn on lock debugging?
(It's applicable instead of the last one.)

--

isicom, fix card locking

- Somebody omitted spin_unlock in interrupt handler and hence card causes
deadlock. Add two unlocks, before returning from handler, if the lock was
acquired before.
- Recursive locking causes deadlock, fix this by avoiding recursion.
Thanks Eric Fox <efox@einsteinindustries.com> for pointing these out.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>

---
commit d1cf4c06710e37fee58dbca38e08b236ba8ff50c
tree da27dc848eb073662174276ab7e0472c9da4193c
parent 1240cd642c42688fab680d1d783eb1821ded9490
author Jiri Slaby <jirislaby@gmail.com> Thu, 07 Dec 2006 17:42:51 +0059
committer Jiri Slaby <jirislaby@gmail.com> Thu, 07 Dec 2006 17:42:51 +0059

drivers/char/isicom.c | 90 ++++++++++++++++++++++++++-----------------------
1 files changed, 47 insertions(+), 43 deletions(-)

diff --git a/drivers/char/isicom.c b/drivers/char/isicom.c
index 1637c1d..adbb16d 100644
--- a/drivers/char/isicom.c
+++ b/drivers/char/isicom.c
@@ -228,6 +228,20 @@ static struct isi_port isi_ports[PORT_C
* it wants to talk.
*/

+static inline int WaitTillCardIsFree(u16 base)
+{
+ unsigned int count = 0;
+ unsigned int a = in_atomic(); /* do we run under spinlock? */
+
+ while (!(inw(base + 0xe) & 0x1) && count++ < 100)
+ if (a)
+ mdelay(1);
+ else
+ msleep(1);
+
+ return !(inw(base + 0xe) & 0x1);
+}
+
static int lock_card(struct isi_board *card)
{
char retries;
@@ -274,69 +288,71 @@ static void unlock_card(struct isi_board
* ISI Card specific ops ...
*/

+/* card->lock HAS to be held */
static void raise_dtr(struct isi_port *port)
{
struct isi_board *card = port->card;
unsigned long base = card->base;
u16 channel = port->channel;

- if (!lock_card(card))
+ if (WaitTillCardIsFree(base))
return;

outw(0x8000 | (channel << card->shift_count) | 0x02, base);
outw(0x0504, base);
InterruptTheCard(base);
port->status |= ISI_DTR;
- unlock_card(card);
}

+/* card->lock HAS to be held */
static inline void drop_dtr(struct isi_port *port)
{
struct isi_board *card = port->card;
unsigned long base = card->base;
u16 channel = port->channel;

- if (!lock_card(card))
+ if (WaitTillCardIsFree(base))
return;

outw(0x8000 | (channel << card->shift_count) | 0x02, base);
outw(0x0404, base);
InterruptTheCard(base);
port->status &= ~ISI_DTR;
- unlock_card(card);
}

+/* card->lock HAS to be held */
static inline void raise_rts(struct isi_port *port)
{
struct isi_board *card = port->card;
unsigned long base = card->base;
u16 channel = port->channel;

- if (!lock_card(card))
+ if (WaitTillCardIsFree(base))
return;

outw(0x8000 | (channel << card->shift_count) | 0x02, base);
outw(0x0a04, base);
InterruptTheCard(base);
port->status |= ISI_RTS;
- unlock_card(card);
}
+
+/* card->lock HAS to be held */
static inline void drop_rts(struct isi_port *port)
{
struct isi_board *card = port->card;
unsigned long base = card->base;
u16 channel = port->channel;

- if (!lock_card(card))
+ if (WaitTillCardIsFree(base))
return;

outw(0x8000 | (channel << card->shift_count) | 0x02, base);
outw(0x0804, base);
InterruptTheCard(base);
port->status &= ~ISI_RTS;
- unlock_card(card);
}

+/* card->lock MUST NOT be held */
static inline void raise_dtr_rts(struct isi_port *port)
{
struct isi_board *card = port->card;
@@ -353,35 +369,20 @@ static inline void raise_dtr_rts(struct
unlock_card(card);
}

+/* card->lock HAS to be held */
static void drop_dtr_rts(struct isi_port *port)
{
struct isi_board *card = port->card;
unsigned long base = card->base;
u16 channel = port->channel;

- if (!lock_card(card))
+ if (WaitTillCardIsFree(base))
return;

outw(0x8000 | (channel << card->shift_count) | 0x02, base);
outw(0x0c04, base);
InterruptTheCard(base);
port->status &= ~(ISI_RTS | ISI_DTR);
- unlock_card(card);
-}
-
-static inline void kill_queue(struct isi_port *port, short queue)
-{
- struct isi_board *card = port->card;
- unsigned long base = card->base;
- u16 channel = port->channel;
-
- if (!lock_card(card))
- return;
-
- outw(0x8000 | (channel << card->shift_count) | 0x02, base);
- outw((queue << 8) | 0x06, base);
- InterruptTheCard(base);
- unlock_card(card);
}

/*
@@ -592,6 +593,7 @@ static irqreturn_t isicom_interrupt(int
ClearInterrupt(base);
else
outw(0x0000, base+0x04); /* enable interrupts */
+ spin_unlock(&card->card_lock);
return IRQ_HANDLED;
}

@@ -712,6 +714,7 @@ static irqreturn_t isicom_interrupt(int
ClearInterrupt(base);
else
outw(0x0000, base+0x04); /* enable interrupts */
+ spin_unlock(&card->card_lock);

return IRQ_HANDLED;
}
@@ -762,7 +765,7 @@ static void isicom_config_port(struct is
else
raise_dtr(port);

- if (lock_card(card)) {
+ if (WaitTillCardIsFree(base) == 0) {
outw(0x8000 | (channel << shift_count) |0x03, base);
outw(linuxb_to_isib[baud] << 8 | 0x03, base);
channel_setup = 0;
@@ -790,7 +793,6 @@ static void isicom_config_port(struct is
}
outw(channel_setup, base);
InterruptTheCard(base);
- unlock_card(card);
}
if (C_CLOCAL(tty))
port->flags &= ~ASYNC_CHECK_CD;
@@ -809,12 +811,11 @@ static void isicom_config_port(struct is
if (I_IXOFF(tty))
flow_ctrl |= ISICOM_INITIATE_XONXOFF;

- if (lock_card(card)) {
+ if (WaitTillCardIsFree(base) == 0) {
outw(0x8000 | (channel << shift_count) |0x04, base);
outw(flow_ctrl << 8 | 0x05, base);
outw((STOP_CHAR(tty)) << 8 | (START_CHAR(tty)), base);
InterruptTheCard(base);
- unlock_card(card);
}

/* rx enabled -> enable port for rx on the card */
@@ -839,10 +840,9 @@ static inline void isicom_setup_board(st
}
port = bp->ports;
bp->status |= BOARD_ACTIVE;
- spin_unlock_irqrestore(&bp->card_lock, flags);
for (channel = 0; channel < bp->port_count; channel++, port++)
drop_dtr_rts(port);
- return;
+ spin_unlock_irqrestore(&bp->card_lock, flags);
}

static int isicom_setup_port(struct isi_port *port)
@@ -875,7 +875,12 @@ static int isicom_setup_port(struct isi_
port->xmit_cnt = port->xmit_head = port->xmit_tail = 0;

/* discard any residual data */
- kill_queue(port, ISICOM_KILLTX | ISICOM_KILLRX);
+ if (WaitTillCardIsFree(card->base) == 0) {
+ outw(0x8000 | (port->channel << card->shift_count) | 0x02,
+ card->base);
+ outw(((ISICOM_KILLTX | ISICOM_KILLRX) << 8) | 0x06, card->base);
+ InterruptTheCard(card->base);
+ }

isicom_config_port(port);
port->flags |= ASYNC_INITIALIZED;
@@ -1030,7 +1035,6 @@ static void isicom_shutdown_port(struct
port->flags &= ~ASYNC_INITIALIZED;
/* 3rd October 2000 : Vinayak P Risbud */
port->tty = NULL;
- spin_unlock_irqrestore(&card->card_lock, flags);

/*Fix done by Anil .S on 30-04-2001
remote login through isi port has dtr toggle problem
@@ -1041,6 +1045,7 @@ static void isicom_shutdown_port(struct
if (C_HUPCL(tty))
/* drop dtr on this port */
drop_dtr(port);
+ spin_unlock_irqrestore(&card->card_lock, flags);

/* any other port uninits */
if (tty)
@@ -1276,10 +1281,12 @@ static int isicom_tiocmset(struct tty_st
unsigned int set, unsigned int clear)
{
struct isi_port *port = tty->driver_data;
+ unsigned long flags;

if (isicom_paranoia_check(port, tty->name, "isicom_ioctl"))
return -ENODEV;

+ spin_lock_irqsave(&port->card->card_lock, flags);
if (set & TIOCM_RTS)
raise_rts(port);
if (set & TIOCM_DTR)
@@ -1289,6 +1296,7 @@ static int isicom_tiocmset(struct tty_st
drop_rts(port);
if (clear & TIOCM_DTR)
drop_dtr(port);
+ spin_unlock_irqrestore(&port->card->card_lock, flags);

return 0;
}
@@ -1321,7 +1329,10 @@ static int isicom_set_serial_info(struct
(newinfo.flags & ASYNC_FLAGS));
}
if (reconfig_port) {
+ unsigned long flags;
+ spin_lock_irqsave(&port->card->card_lock, flags);
isicom_config_port(port);
+ spin_unlock_irqrestore(&port->card->card_lock, flags);
}
return 0;
}
@@ -1402,6 +1413,7 @@ static void isicom_set_termios(struct tt
struct termios *old_termios)
{
struct isi_port *port = tty->driver_data;
+ unsigned long flags;

if (isicom_paranoia_check(port, tty->name, "isicom_set_termios"))
return;
@@ -1410,7 +1422,9 @@ static void isicom_set_termios(struct tt
tty->termios->c_iflag == old_termios->c_iflag)
return;

+ spin_lock_irqsave(&port->card->card_lock, flags);
isicom_config_port(port);
+ spin_unlock_irqrestore(&port->card->card_lock, flags);

if ((old_termios->c_cflag & CRTSCTS) &&
!(tty->termios->c_cflag & CRTSCTS)) {
@@ -1704,16 +1718,6 @@ end:
return retval;
}

-static inline int WaitTillCardIsFree(u16 base)
-{
- unsigned long count = 0;
-
- while (!(inw(base + 0xe) & 0x1) && count++ < 100)
- msleep(5);
-
- return !(inw(base + 0xe) & 0x1);
-}
-
static int __devinit load_firmware(struct pci_dev *pdev,
const unsigned int index, const unsigned int signature)
{
-
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