[PATCH net] net: dm9000: Fix a recursive lockup in the TX timeout path

[Ginger Li <ginger.jzllee@gmail.com>]

dm9000_timeout() takes db->lock with interrupts disabled and then calls
dm9000_init_dm9000(), which expects the caller to hold that lock and accesses
the chip registers directly.  For DM9000B devices dm9000_init_dm9000() also
calls dm9000_phy_write(), and that function takes db->lock again, so the TX
timeout path deadlocks on the same CPU.

dm9000_phy_write() already skips db->addr_lock when db->in_timeout is set,
because in that case the caller holds db->lock and sleeping is not allowed
either.  Skip db->lock as well then, so that the nested call from
dm9000_init_dm9000() works as intended.

Fixes: 6741f40 ("DM9000B: driver initialization upgrade")
Signed-off-by: Ginger Li <ginger.jzllee@gmail.com>
---
 drivers/net/ethernet/davicom/dm9000.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/davicom/dm9000.c b/drivers/net/ethernet/davicom/dm9000.c
--- a/drivers/net/ethernet/davicom/dm9000.c
+++ b/drivers/net/ethernet/davicom/dm9000.c
@@ -325,10 +325,10 @@ dm9000_phy_write(struct net_device *dev,
 	unsigned long reg_save;
 
 	dm9000_dbg(db, 5, "phy_write[%02x] = %04x\n", reg, value);
-	if (!db->in_timeout)
+	if (!db->in_timeout) {
 		mutex_lock(&db->addr_lock);
-
-	spin_lock_irqsave(&db->lock, flags);
+		spin_lock_irqsave(&db->lock, flags);
+	}
 
 	/* Save previous register address */
 	reg_save = readb(db->io_addr);
@@ -344,11 +344,14 @@ dm9000_phy_write(struct net_device *dev,
 	iow(db, DM9000_EPCR, EPCR_EPOS | EPCR_ERPRW);
 
 	writeb(reg_save, db->io_addr);
-	spin_unlock_irqrestore(&db->lock, flags);
+	if (!db->in_timeout)
+		spin_unlock_irqrestore(&db->lock, flags);
 
 	dm9000_msleep(db, 1);		/* Wait write complete */
 
-	spin_lock_irqsave(&db->lock, flags);
+	if (!db->in_timeout)
+		spin_lock_irqsave(&db->lock, flags);
+
 	reg_save = readb(db->io_addr);
 
 	iow(db, DM9000_EPCR, 0x0);	/* Clear phyxcer write command */
@@ -356,9 +359,10 @@ dm9000_phy_write(struct net_device *dev,
 	/* restore the previous address */
 	writeb(reg_save, db->io_addr);
 
-	spin_unlock_irqrestore(&db->lock, flags);
-	if (!db->in_timeout)
+	if (!db->in_timeout) {
+		spin_unlock_irqrestore(&db->lock, flags);
 		mutex_unlock(&db->addr_lock);
+	}
 }
 
 /* dm9000_set_io
-- 
2.43.0