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CAPI: Fix locking around capiminor's output queue and drop workaround…
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…_lock

Introduce outlock as a spin lock that protects capiminor's outqueue,
outbytes and outskb (formerly known as ttyskb). outlock can be acquired
from soft-IRQ context via capinc_write, so make it bh-safe.

This finally removes the last reason for keeping the workaround lock
around (which was incomplete and partly broken anyway). And as we no
longer call handle_recv_skb in atomic context, gen_data_b3_resp_for can
use non-atomic allocation now.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Jan Kiszka authored and David S. Miller committed Feb 17, 2010
1 parent 68d7347 commit dfbb84f
Showing 1 changed file with 67 additions and 59 deletions.
126 changes: 67 additions & 59 deletions drivers/isdn/capi/capi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -95,27 +95,20 @@ struct capiminor {
struct tty_port port;
int ttyinstop;
int ttyoutstop;
struct sk_buff *ttyskb;

struct sk_buff_head inqueue;
struct sk_buff_head outqueue;
int outbytes;
struct sk_buff_head inqueue;

struct sk_buff_head outqueue;
int outbytes;
struct sk_buff *outskb;
spinlock_t outlock;

/* transmit path */
struct list_head ackqueue;
int nack;
spinlock_t ackqlock;
};

/* FIXME: The following lock is a sledgehammer-workaround to a
* locking issue with the capiminor (and maybe other) data structure(s).
* Access to this data is done in a racy way and crashes the machine with
* a FritzCard DSL driver; sooner or later. This is a workaround
* which trades scalability vs stability, so it doesn't crash the kernel anymore.
* The correct (and scalable) fix for the issue seems to require
* an API change to the drivers... . */
static DEFINE_SPINLOCK(workaround_lock);

struct capincci {
struct list_head list;
u32 ncci;
Expand Down Expand Up @@ -231,6 +224,7 @@ static struct capiminor *capiminor_alloc(struct capi20_appl *ap, u32 ncci)

skb_queue_head_init(&mp->inqueue);
skb_queue_head_init(&mp->outqueue);
spin_lock_init(&mp->outlock);

tty_port_init(&mp->port);
mp->port.ops = &capiminor_port_ops;
Expand Down Expand Up @@ -271,7 +265,7 @@ static void capiminor_destroy(struct kref *kref)
{
struct capiminor *mp = container_of(kref, struct capiminor, kref);

kfree_skb(mp->ttyskb);
kfree_skb(mp->outskb);
skb_queue_purge(&mp->inqueue);
skb_queue_purge(&mp->outqueue);
capiminor_del_all_ack(mp);
Expand Down Expand Up @@ -417,7 +411,7 @@ static struct sk_buff *
gen_data_b3_resp_for(struct capiminor *mp, struct sk_buff *skb)
{
struct sk_buff *nskb;
nskb = alloc_skb(CAPI_DATA_B3_RESP_LEN, GFP_ATOMIC);
nskb = alloc_skb(CAPI_DATA_B3_RESP_LEN, GFP_KERNEL);
if (nskb) {
u16 datahandle = CAPIMSG_U16(skb->data,CAPIMSG_BASELEN+4+4+2);
unsigned char *s = skb_put(nskb, CAPI_DATA_B3_RESP_LEN);
Expand Down Expand Up @@ -548,9 +542,18 @@ static int handle_minor_send(struct capiminor *mp)
return 0;
}

while ((skb = skb_dequeue(&mp->outqueue)) != NULL) {
datahandle = atomic_inc_return(&mp->datahandle);
while (1) {
spin_lock_bh(&mp->outlock);
skb = __skb_dequeue(&mp->outqueue);
if (!skb) {
spin_unlock_bh(&mp->outlock);
break;
}
len = (u16)skb->len;
mp->outbytes -= len;
spin_unlock_bh(&mp->outlock);

datahandle = atomic_inc_return(&mp->datahandle);
skb_push(skb, CAPI_DATA_B3_REQ_LEN);
memset(skb->data, 0, CAPI_DATA_B3_REQ_LEN);
capimsg_setu16(skb->data, 0, CAPI_DATA_B3_REQ_LEN);
Expand All @@ -566,14 +569,18 @@ static int handle_minor_send(struct capiminor *mp)

if (capiminor_add_ack(mp, datahandle) < 0) {
skb_pull(skb, CAPI_DATA_B3_REQ_LEN);
skb_queue_head(&mp->outqueue, skb);

spin_lock_bh(&mp->outlock);
__skb_queue_head(&mp->outqueue, skb);
mp->outbytes += len;
spin_unlock_bh(&mp->outlock);

tty_kref_put(tty);
return count;
}
errcode = capi20_put_message(mp->ap, skb);
if (errcode == CAPI_NOERROR) {
count++;
mp->outbytes -= len;
#ifdef _DEBUG_DATAFLOW
printk(KERN_DEBUG "capi: DATA_B3_REQ %u len=%u\n",
datahandle, len);
Expand All @@ -584,13 +591,17 @@ static int handle_minor_send(struct capiminor *mp)

if (errcode == CAPI_SENDQUEUEFULL) {
skb_pull(skb, CAPI_DATA_B3_REQ_LEN);
skb_queue_head(&mp->outqueue, skb);

spin_lock_bh(&mp->outlock);
__skb_queue_head(&mp->outqueue, skb);
mp->outbytes += len;
spin_unlock_bh(&mp->outlock);

break;
}

/* ups, drop packet */
printk(KERN_ERR "capi: put_message = %x\n", errcode);
mp->outbytes -= len;
kfree_skb(skb);
}
tty_kref_put(tty);
Expand All @@ -609,7 +620,6 @@ static void capi_recv_message(struct capi20_appl *ap, struct sk_buff *skb)
u16 datahandle;
#endif /* CONFIG_ISDN_CAPI_MIDDLEWARE */
struct capincci *np;
unsigned long flags;

mutex_lock(&cdev->lock);

Expand All @@ -621,7 +631,6 @@ static void capi_recv_message(struct capi20_appl *ap, struct sk_buff *skb)
if (CAPIMSG_CMD(skb->data) == CAPI_CONNECT_B3_IND)
capincci_alloc(cdev, CAPIMSG_NCCI(skb->data));

spin_lock_irqsave(&workaround_lock, flags);
if (CAPIMSG_COMMAND(skb->data) != CAPI_DATA_B3) {
skb_queue_tail(&cdev->recvqueue, skb);
wake_up_interruptible(&cdev->recvwait);
Expand Down Expand Up @@ -683,7 +692,6 @@ static void capi_recv_message(struct capi20_appl *ap, struct sk_buff *skb)
#endif /* CONFIG_ISDN_CAPI_MIDDLEWARE */

unlock_out:
spin_unlock_irqrestore(&workaround_lock, flags);
mutex_unlock(&cdev->lock);
}

Expand Down Expand Up @@ -1062,16 +1070,13 @@ static void capinc_tty_cleanup(struct tty_struct *tty)
static int capinc_tty_open(struct tty_struct *tty, struct file *filp)
{
struct capiminor *mp = tty->driver_data;
unsigned long flags;
int err;

err = tty_port_open(&mp->port, tty, filp);
if (err)
return err;

spin_lock_irqsave(&workaround_lock, flags);
handle_minor_recv(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
return 0;
}

Expand All @@ -1087,94 +1092,103 @@ static int capinc_tty_write(struct tty_struct *tty,
{
struct capiminor *mp = tty->driver_data;
struct sk_buff *skb;
unsigned long flags;

#ifdef _DEBUG_TTYFUNCS
printk(KERN_DEBUG "capinc_tty_write(count=%d)\n", count);
#endif

spin_lock_irqsave(&workaround_lock, flags);
skb = mp->ttyskb;
spin_lock_bh(&mp->outlock);
skb = mp->outskb;
if (skb) {
mp->ttyskb = NULL;
skb_queue_tail(&mp->outqueue, skb);
mp->outskb = NULL;
__skb_queue_tail(&mp->outqueue, skb);
mp->outbytes += skb->len;
}

skb = alloc_skb(CAPI_DATA_B3_REQ_LEN+count, GFP_ATOMIC);
if (!skb) {
printk(KERN_ERR "capinc_tty_write: alloc_skb failed\n");
spin_unlock_irqrestore(&workaround_lock, flags);
spin_unlock_bh(&mp->outlock);
return -ENOMEM;
}

skb_reserve(skb, CAPI_DATA_B3_REQ_LEN);
memcpy(skb_put(skb, count), buf, count);

skb_queue_tail(&mp->outqueue, skb);
__skb_queue_tail(&mp->outqueue, skb);
mp->outbytes += skb->len;
spin_unlock_bh(&mp->outlock);

(void)handle_minor_send(mp);
spin_unlock_irqrestore(&workaround_lock, flags);

return count;
}

static int capinc_tty_put_char(struct tty_struct *tty, unsigned char ch)
{
struct capiminor *mp = tty->driver_data;
bool invoke_send = false;
struct sk_buff *skb;
unsigned long flags;
int ret = 1;

#ifdef _DEBUG_TTYFUNCS
printk(KERN_DEBUG "capinc_put_char(%u)\n", ch);
#endif

spin_lock_irqsave(&workaround_lock, flags);
skb = mp->ttyskb;
spin_lock_bh(&mp->outlock);
skb = mp->outskb;
if (skb) {
if (skb_tailroom(skb) > 0) {
*(skb_put(skb, 1)) = ch;
spin_unlock_irqrestore(&workaround_lock, flags);
return 1;
goto unlock_out;
}
mp->ttyskb = NULL;
skb_queue_tail(&mp->outqueue, skb);
mp->outskb = NULL;
__skb_queue_tail(&mp->outqueue, skb);
mp->outbytes += skb->len;
(void)handle_minor_send(mp);
invoke_send = true;
}

skb = alloc_skb(CAPI_DATA_B3_REQ_LEN+CAPI_MAX_BLKSIZE, GFP_ATOMIC);
if (skb) {
skb_reserve(skb, CAPI_DATA_B3_REQ_LEN);
*(skb_put(skb, 1)) = ch;
mp->ttyskb = skb;
mp->outskb = skb;
} else {
printk(KERN_ERR "capinc_put_char: char %u lost\n", ch);
ret = 0;
}
spin_unlock_irqrestore(&workaround_lock, flags);

unlock_out:
spin_unlock_bh(&mp->outlock);

if (invoke_send)
(void)handle_minor_send(mp);

return ret;
}

static void capinc_tty_flush_chars(struct tty_struct *tty)
{
struct capiminor *mp = tty->driver_data;
struct sk_buff *skb;
unsigned long flags;

#ifdef _DEBUG_TTYFUNCS
printk(KERN_DEBUG "capinc_tty_flush_chars\n");
#endif

spin_lock_irqsave(&workaround_lock, flags);
skb = mp->ttyskb;
spin_lock_bh(&mp->outlock);
skb = mp->outskb;
if (skb) {
mp->ttyskb = NULL;
skb_queue_tail(&mp->outqueue, skb);
mp->outskb = NULL;
__skb_queue_tail(&mp->outqueue, skb);
mp->outbytes += skb->len;
spin_unlock_bh(&mp->outlock);

(void)handle_minor_send(mp);
}
(void)handle_minor_recv(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
} else
spin_unlock_bh(&mp->outlock);

handle_minor_recv(mp);
}

static int capinc_tty_write_room(struct tty_struct *tty)
Expand Down Expand Up @@ -1234,15 +1248,12 @@ static void capinc_tty_throttle(struct tty_struct *tty)
static void capinc_tty_unthrottle(struct tty_struct *tty)
{
struct capiminor *mp = tty->driver_data;
unsigned long flags;

#ifdef _DEBUG_TTYFUNCS
printk(KERN_DEBUG "capinc_tty_unthrottle\n");
#endif
spin_lock_irqsave(&workaround_lock, flags);
mp->ttyinstop = 0;
handle_minor_recv(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
}

static void capinc_tty_stop(struct tty_struct *tty)
Expand All @@ -1258,15 +1269,12 @@ static void capinc_tty_stop(struct tty_struct *tty)
static void capinc_tty_start(struct tty_struct *tty)
{
struct capiminor *mp = tty->driver_data;
unsigned long flags;

#ifdef _DEBUG_TTYFUNCS
printk(KERN_DEBUG "capinc_tty_start\n");
#endif
spin_lock_irqsave(&workaround_lock, flags);
mp->ttyoutstop = 0;
(void)handle_minor_send(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
}

static void capinc_tty_hangup(struct tty_struct *tty)
Expand Down

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