[PATCH 1/1 v3] Char: isicom, fix card locking

From: Jiri Slaby
Date: Fri Dec 08 2006 - 19:45:51 EST

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me wrote:
> If nothing appeared in dmesg (even before setserial) and the second option is
> enabled, then I'm out of clues for now (however I revealed another recursive
> locking issue in close() function). Could you apply this dirty hack

Ok, this third version covers the revealed recursion. Could you test it?

--

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 when _open and _close is called on SMP
machine, fix this by avoiding recursion.
Thanks Eric Fox <efox@xxxxxxxxxxxxxxxxxxxxxx> for pointing these out.

Signed-off-by: Jiri Slaby <jirislaby@xxxxxxxxx>

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

isicom.c | 105 +++++++++++++++++++++++++++++++--------------------------------
1 file changed, 53 insertions(+), 52 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;
@@ -1001,28 +1006,22 @@ static int isicom_open(struct tty_struct

static inline void isicom_shutdown_board(struct isi_board *bp)
{
- unsigned long flags;
-
- spin_lock_irqsave(&bp->card_lock, flags);
if (bp->status & BOARD_ACTIVE) {
bp->status &= ~BOARD_ACTIVE;
}
- spin_unlock_irqrestore(&bp->card_lock, flags);
}

+/* card->lock HAS to be held */
static void isicom_shutdown_port(struct isi_port *port)
{
struct isi_board *card = port->card;
struct tty_struct *tty;
- unsigned long flags;

tty = port->tty;

- spin_lock_irqsave(&card->card_lock, flags);
- if (!(port->flags & ASYNC_INITIALIZED)) {
- spin_unlock_irqrestore(&card->card_lock, flags);
+ if (!(port->flags & ASYNC_INITIALIZED))
return;
- }
+
if (port->xmit_buf) {
free_page((unsigned long) port->xmit_buf);
port->xmit_buf = NULL;
@@ -1030,7 +1029,6 @@ 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
@@ -1276,10 +1274,12 @@ 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 +1289,7 @@ 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 +1322,10 @@ 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 +1406,7 @@ 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 +1415,9 @@ 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)) {
@@ -1487,11 +1494,15 @@ static void do_isicom_hangup(struct work
static void isicom_hangup(struct tty_struct *tty)
{
struct isi_port *port = tty->driver_data;
+ unsigned long flags;

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

+ spin_lock_irqsave(&port->card->card_lock, flags);
isicom_shutdown_port(port);
+ spin_unlock_irqrestore(&port->card->card_lock, flags);
+
port->count = 0;
port->flags &= ~ASYNC_NORMAL_ACTIVE;
port->tty = NULL;
@@ -1704,16 +1715,6 @@ 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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Next message: Ben Collins: "Re: [PATCH] PCI legacy resource fix"
Previous message: Seth Arnold: "Re: [PATCH 0/2] file capabilities: two bugfixes"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]