From dfbb84ffe94e75e2d56250fa948db40f6c62093f Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 8 Feb 2010 10:12:40 +0000 Subject: [PATCH] CAPI: Fix locking around capiminor's output queue and drop workaround_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 Signed-off-by: David S. Miller --- drivers/isdn/capi/capi.c | 126 +++++++++++++++++++++++++---------------------- 1 file changed, 67 insertions(+), 59 deletions(-) diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c index be85c8c1e8b4..074496fae8da 100644 --- a/drivers/isdn/capi/capi.c +++ b/drivers/isdn/capi/capi.c @@ -95,11 +95,13 @@ 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; @@ -107,15 +109,6 @@ struct capiminor { 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; @@ -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; @@ -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); @@ -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); @@ -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); @@ -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); @@ -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); @@ -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); @@ -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); @@ -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); } @@ -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; } @@ -1087,71 +1092,78 @@ 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; } @@ -1159,22 +1171,24 @@ 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) @@ -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) @@ -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) -- 2.11.0