lkml.org 
[lkml]   [2010]   [Jan]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 22/31] CAPI: Rework tty locking in RX and TX path of capiminor
Introduce a mutex called ttylock to make handle_recv_skb atomic /wrt
parallel invocations as well as capinc_tty_close clearing the tty_struct
reference. Also avoid re-queuing skbs unless the error detected in
handle_recv_skb is expected to be recoverable such as lacking memory, a
full CAPI queue, or a full TTY input buffer.

As we expect to be in thread context in handle_recv_skb, we must neither
call this function from potenially atomic capinc_tty_write nor while
holding the workaround_lock. For the same reason, we do not need to
allocate skbs atomically in gen_data_b3_resp_for.

The ttylock is also used to avoid waking up a non-existent TTY in
capi_recv_message.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
---
drivers/isdn/capi/capi.c | 90 ++++++++++++++++++++++++++++------------------
1 files changed, 55 insertions(+), 35 deletions(-)
diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c
index 77faa4e..e880639 100644
--- a/drivers/isdn/capi/capi.c
+++ b/drivers/isdn/capi/capi.c
@@ -93,9 +93,10 @@ struct capiminor {
u16 datahandle;
u16 msgid;

- struct tty_struct *tty;
- int ttyinstop;
- int ttyoutstop;
+ struct tty_struct *tty;
+ struct mutex ttylock;
+ int ttyinstop;
+ int ttyoutstop;
struct sk_buff *ttyskb;

struct sk_buff_head inqueue;
@@ -228,6 +229,8 @@ static struct capiminor *capiminor_alloc(struct capi20_appl *ap, u32 ncci)
skb_queue_head_init(&mp->inqueue);
skb_queue_head_init(&mp->outqueue);

+ mutex_init(&mp->ttylock);
+
/* Allocate the least unused minor number.
*/
if (list_empty(&capiminor_list))
@@ -385,7 +388,7 @@ 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);
@@ -406,61 +409,74 @@ static int handle_recv_skb(struct capiminor *mp, struct sk_buff *skb)
int datalen;
u16 errcode, datahandle;
struct tty_ldisc *ld;
-
- datalen = skb->len - CAPIMSG_LEN(skb->data);
- if (mp->tty == NULL)
- {
+ int ret = -1;
+
+ mutex_lock(&mp->ttylock);
+
+ if (!mp->tty) {
#ifdef _DEBUG_DATAFLOW
printk(KERN_DEBUG "capi: currently no receivern");
#endif
+ mutex_unlock(&mp->ttylock);
return -1;
}

ld = tty_ldisc_ref(mp->tty);
- if (ld == NULL)
- return -1;
- if (ld->ops->receive_buf == NULL) {
+ if (!ld || !ld->ops->receive_buf) {
#if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
- printk(KERN_DEBUG "capi: ldisc has no receive_buf functionn");
+ printk(KERN_DEBUG "capi: no ldisc or receive_buf functionn");
#endif
- goto bad;
+ ret = 0;
+ goto drop;
}
if (mp->ttyinstop) {
#if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
printk(KERN_DEBUG "capi: recv tty throttledn");
#endif
- goto bad;
+ goto keep;
}
+
+ datalen = skb->len - CAPIMSG_LEN(skb->data);
if (mp->tty->receive_room < datalen) {
#if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
printk(KERN_DEBUG "capi: no room in ttyn");
#endif
- goto bad;
+ goto keep;
}
- if ((nskb = gen_data_b3_resp_for(mp, skb)) == NULL) {
+
+ nskb = gen_data_b3_resp_for(mp, skb);
+ if (!nskb) {
printk(KERN_ERR "capi: gen_data_b3_resp failedn");
- goto bad;
+ goto keep;
}
+
datahandle = CAPIMSG_U16(skb->data,CAPIMSG_BASELEN+4);
+
errcode = capi20_put_message(mp->ap, nskb);
- if (errcode != CAPI_NOERROR) {
+
+ if (errcode == CAPI_NOERROR) {
+ skb_pull(skb, CAPIMSG_LEN(skb->data));
+#ifdef _DEBUG_DATAFLOW
+ printk(KERN_DEBUG "capi: DATA_B3_RESP %u len=%d => ldiscn",
+ datahandle, skb->len);
+#endif
+ ld->ops->receive_buf(mp->tty, skb->data, NULL, skb->len);
+ } else {
printk(KERN_ERR "capi: send DATA_B3_RESP failed=%xn",
errcode);
kfree_skb(nskb);
- goto bad;
+
+ if (errcode == CAPI_SENDQUEUEFULL)
+ goto keep;
}
- (void)skb_pull(skb, CAPIMSG_LEN(skb->data));
-#ifdef _DEBUG_DATAFLOW
- printk(KERN_DEBUG "capi: DATA_B3_RESP %u len=%d => ldiscn",
- datahandle, skb->len);
-#endif
- ld->ops->receive_buf(mp->tty, skb->data, NULL, skb->len);
+ ret = 0;
+
+drop:
kfree_skb(skb);
+keep:
tty_ldisc_deref(ld);
- return 0;
-bad:
- tty_ldisc_deref(ld);
- return -1;
+ mutex_unlock(&mp->ttylock);
+ return ret;
}

static void handle_minor_recv(struct capiminor *mp)
@@ -610,8 +626,10 @@ static void capi_recv_message(struct capi20_appl *ap, struct sk_buff *skb)
#endif
kfree_skb(skb);
(void)capiminor_del_ack(mp, datahandle);
+ mutex_lock(&mp->ttylock);
if (mp->tty)
tty_wakeup(mp->tty);
+ mutex_unlock(&mp->ttylock);
(void)handle_minor_send(mp);

} else {
@@ -1006,8 +1024,12 @@ static void capinc_tty_close(struct tty_struct * tty, struct file * file)

mutex_lock(&glue_lock);

- if (tty->count == 1)
+ if (tty->count == 1) {
+ mutex_lock(&mp->ttylock);
mp->tty = NULL;
+ mutex_unlock(&mp->ttylock);
+ }
+
if (!mp->nccip)
capiminor_free(mp);

@@ -1046,7 +1068,6 @@ static int capinc_tty_write(struct tty_struct * tty,
skb_queue_tail(&mp->outqueue, skb);
mp->outbytes += skb->len;
(void)handle_minor_send(mp);
- (void)handle_minor_recv(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
return count;
}
@@ -1106,8 +1127,9 @@ static void capinc_tty_flush_chars(struct tty_struct *tty)
mp->outbytes += skb->len;
(void)handle_minor_send(mp);
}
- (void)handle_minor_recv(mp);
spin_unlock_irqrestore(&workaround_lock, flags);
+
+ handle_minor_recv(mp);
}

static int capinc_tty_write_room(struct tty_struct *tty)
@@ -1167,14 +1189,12 @@ 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_unthrottlen");
#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)
--
1.6.0.2


\
 
 \ /
  Last update: 2010-01-23 00:29    [from the cache]
©2003-2011 Jasper Spaans