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Message-Id: <0c53b516bac19ca785b0a8e9ada7bcb6970fda5b.1579730846.git.fthain@telegraphics.com.au>
Date: Thu, 23 Jan 2020 09:07:26 +1100
From: Finn Thain <fthain@...egraphics.com.au>
To: "David S. Miller" <davem@...emloft.net>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Chris Zankel <chris@...kel.net>,
Laurent Vivier <laurent@...ier.eu>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Eric Dumazet <eric.dumazet@...il.com>,
Stephen Hemminger <stephen@...workplumber.org>,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net v3 01/12] 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: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update")
Tested-by: Stan Johnson <userm57@...oo.com>
Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
---
Changed since v1:
- Added spin lock, as requested by Geert.
Changed since v2:
- Added comment to explain the need for an irq lock.
---
drivers/net/ethernet/natsemi/sonic.c | 49 ++++++++++++++++++++--------
drivers/net/ethernet/natsemi/sonic.h | 1 +
2 files changed, 36 insertions(+), 14 deletions(-)
diff --git a/drivers/net/ethernet/natsemi/sonic.c b/drivers/net/ethernet/natsemi/sonic.c
index b339125b2f09..8a7cff516281 100644
--- a/drivers/net/ethernet/natsemi/sonic.c
+++ b/drivers/net/ethernet/natsemi/sonic.c
@@ -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;
}
diff --git a/drivers/net/ethernet/natsemi/sonic.h b/drivers/net/ethernet/natsemi/sonic.h
index 2b27f7049acb..f9506863e9d1 100644
--- a/drivers/net/ethernet/natsemi/sonic.h
+++ b/drivers/net/ethernet/natsemi/sonic.h
@@ -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)
--
2.24.1
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