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net/sonic: Add mutual exclusion for accessing shared state 

The netif_stop_queue() call in sonic_send_packet() races with the
netif_wake_queue() call in sonic_interrupt(). This causes issues
like "NETDEV WATCHDOG: eth0 (macsonic): transmit queue 0 timed out".
Fix this by disabling interrupts when accessing tx_skb[] and next_tx.
Update a comment to clarify the synchronization properties.

Fixes: efcce83936 ("[PATCH] macsonic/jazzsonic network drivers update")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
alistair/sunxi64-5.5-dsi
Finn Thain 2020-01-23 09:07:26 +11:00 committed by David S. Miller
parent 457bfc0a4b
commit 865ad2f220
2 changed files with 36 additions and 14 deletions
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49
drivers/net/ethernet/natsemi/sonic.c
View File

@ -64,6 +64,8 @@ static int sonic_open(struct net_device *dev)
netif_dbg(lp, ifup, dev, "%s: initializing sonic driver\n", __func__);
spin_lock_init(&lp->lock);
for (i = 0; i < SONIC_NUM_RRS; i++) {
struct sk_buff *skb = netdev_alloc_skb(dev, SONIC_RBSIZE + 2);
if (skb == NULL) {
@ -206,8 +208,6 @@ static void sonic_tx_timeout(struct net_device *dev)
* wake the tx queue
* Concurrently with all of this, the SONIC is potentially writing to
* the status flags of the TDs.
* Until some mutual exclusion is added, this code will not work with SMP. However,
* MIPS Jazz machines and m68k Macs were all uni-processor machines.
*/
static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
@ -215,7 +215,8 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
struct sonic_local *lp = netdev_priv(dev);
dma_addr_t laddr;
int length;
int entry = lp->next_tx;
int entry;
unsigned long flags;
netif_dbg(lp, tx_queued, dev, "%s: skb=%p\n", __func__, skb);
@ -237,6 +238,10 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_OK;
}
spin_lock_irqsave(&lp->lock, flags);
entry = lp->next_tx;
sonic_tda_put(dev, entry, SONIC_TD_STATUS, 0); /* clear status */
sonic_tda_put(dev, entry, SONIC_TD_FRAG_COUNT, 1); /* single fragment */
sonic_tda_put(dev, entry, SONIC_TD_PKTSIZE, length); /* length of packet */
@ -246,10 +251,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
sonic_tda_put(dev, entry, SONIC_TD_LINK,
sonic_tda_get(dev, entry, SONIC_TD_LINK) | SONIC_EOL);
/*
* Must set tx_skb[entry] only after clearing status, and
* before clearing EOL and before stopping queue
*/
wmb();
lp->tx_len[entry] = length;
lp->tx_laddr[entry] = laddr;
@ -272,6 +273,8 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
SONIC_WRITE(SONIC_CMD, SONIC_CR_TXP);
spin_unlock_irqrestore(&lp->lock, flags);
return NETDEV_TX_OK;
}
@ -284,9 +287,21 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
struct net_device *dev = dev_id;
struct sonic_local *lp = netdev_priv(dev);
int status;
unsigned long flags;
/* The lock has two purposes. Firstly, it synchronizes sonic_interrupt()
* with sonic_send_packet() so that the two functions can share state.
* Secondly, it makes sonic_interrupt() re-entrant, as that is required
* by macsonic which must use two IRQs with different priority levels.
*/
spin_lock_irqsave(&lp->lock, flags);
status = SONIC_READ(SONIC_ISR) & SONIC_IMR_DEFAULT;
if (!status) {
spin_unlock_irqrestore(&lp->lock, flags);
if (!(status = SONIC_READ(SONIC_ISR) & SONIC_IMR_DEFAULT))
return IRQ_NONE;
}
do {
if (status & SONIC_INT_PKTRX) {
@ -300,11 +315,12 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
int td_status;
int freed_some = 0;
/* At this point, cur_tx is the index of a TD that is one of:
* unallocated/freed (status set & tx_skb[entry] clear)
* allocated and sent (status set & tx_skb[entry] set )
* allocated and not yet sent (status clear & tx_skb[entry] set )
* still being allocated by sonic_send_packet (status clear & tx_skb[entry] clear)
/* The state of a Transmit Descriptor may be inferred
* from { tx_skb[entry], td_status } as follows.
* { clear, clear } => the TD has never been used
* { set, clear } => the TD was handed to SONIC
* { set, set } => the TD was handed back
* { clear, set } => the TD is available for re-use
*/
netif_dbg(lp, intr, dev, "%s: tx done\n", __func__);
@ -406,7 +422,12 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
/* load CAM done */
if (status & SONIC_INT_LCD)
SONIC_WRITE(SONIC_ISR, SONIC_INT_LCD); /* clear the interrupt */
} while((status = SONIC_READ(SONIC_ISR) & SONIC_IMR_DEFAULT));
status = SONIC_READ(SONIC_ISR) & SONIC_IMR_DEFAULT;
} while (status);
spin_unlock_irqrestore(&lp->lock, flags);
return IRQ_HANDLED;
}

1
drivers/net/ethernet/natsemi/sonic.h
View File

@ -322,6 +322,7 @@ struct sonic_local {
int msg_enable;
struct device *device; /* generic device */
struct net_device_stats stats;
spinlock_t lock;
};
#define TX_TIMEOUT (3 * HZ)