[PATCH v3 1/2] drivers: net: sun4i-emac: Fix double spinlock in emac_timeout

[qianfanguijin at 163.com]

From: qianfan Zhao <qianfanguijin at 163.com>

emac_timeout() callback acquires lock and so does emac_init_device(),
which called inside lock protected region. This hangs the system and
produces following warning:

WARNING: CPU: 2 PID: 0 at net/sched/sch_generic.c:478
dev_watchdog+0x2e4/0x2e8
NETDEV WATCHDOG: FE0 (sun4i-emac): transmit queue 0 timed out
Modules linked in:
CPU: 2 PID: 0 Comm: swapper/2 Tainted: G W 5.15.0-00047-g0848e4aeb313
Hardware name: Wisdom T3 based CCT Family
[<c010f740>] (unwind_backtrace) from [<c010b744>] (show_stack+0x10/0x14)
[<c010b744>] (show_stack) from [<c0a4d978>] (dump_stack_lvl+0x40/0x4c)
[<c0a4d978>] (dump_stack_lvl) from [<c0120734>] (__warn+0x104/0x108)
[<c0120734>] (__warn) from [<c01207b0>] (warn_slowpath_fmt+0x78/0xbc)
[<c01207b0>] (warn_slowpath_fmt) from [<c0898a54>]
(dev_watchdog+0x2e4/0x2e8)
[<c0898a54>] (dev_watchdog) from [<c019a888>] (call_timer_fn+0x3c/0x178)
[<c019a888>] (call_timer_fn) from [<c019bddc>]
(run_timer_softirq+0x540/0x624)
[<c019bddc>] (run_timer_softirq) from [<c0101298>]
(__do_softirq+0x130/0x3bc)
[<c0101298>] (__do_softirq) from [<c0127ea0>] (irq_exit+0xbc/0x100)
[<c0127ea0>] (irq_exit) from [<c017e514>] (handle_domain_irq+0x60/0x78)
[<c017e514>] (handle_domain_irq) from [<c05a6130>]
(gic_handle_irq+0x7c/0x90)
[<c05a6130>] (gic_handle_irq) from [<c0100afc>] (__irq_svc+0x5c/0x78)
Exception stack(0xc14f3f70 to 0xc14f3fb8)
3f60:                                     0003475c 00000000 00000001
c01188a0
3f80: c107b200 c0f06b4c c0f06b90 00000004 c1079ff8 c0c62774 00000000
00000000
3fa0: c10b2198 c14f3fc0 c0107fcc c0107fd0 60030013 ffffffff
[<c0100afc>] (__irq_svc) from [<c0107fd0>] (arch_cpu_idle+0x38/0x3c)
[<c0107fd0>] (arch_cpu_idle) from [<c0a57f38>]
(default_idle_call+0x3c/0xcc)
[<c0a57f38>] (default_idle_call) from [<c0157258>] (do_idle+0xdc/0x13c)
[<c0157258>] (do_idle) from [<c01575a4>] (cpu_startup_entry+0x18/0x1c)
[<c01575a4>] (cpu_startup_entry) from [<401015d0>] (0x401015d0)
---[ end trace a70942a1265338f1 ]---
rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
rcu: \x092-...0: (1 GPs behind) idle=75d/0/0x1 softirq=8288/8289 fqs=931
\x09(detected by 0, t=2102 jiffies, g=13485, q=1635)
Sending NMI from CPU 0 to CPUs 2:
spi_master spi2: spi2.1: timeout transferring 4 bytes at 100000Hz for
110(100)ms
spidev spi2.1: SPI transfer failed: -110

Fixes: 492205050d77b (net: Add EMAC ethernet driver found on Allwinner A10 SoC's)
Signed-off-by: qianfan Zhao <qianfanguijin at 163.com>
---
 drivers/net/ethernet/allwinner/sun4i-emac.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/allwinner/sun4i-emac.c b/drivers/net/ethernet/allwinner/sun4i-emac.c
index a94c62956eed..8093d6d2101c 100644
--- a/drivers/net/ethernet/allwinner/sun4i-emac.c
+++ b/drivers/net/ethernet/allwinner/sun4i-emac.c
@@ -488,14 +488,11 @@ static int emac_set_mac_address(struct net_device *dev, void *p)
 }
 
 /* Initialize emac board */
-static void emac_init_device(struct net_device *dev)
+static void emac_init_device_no_lock(struct net_device *dev)
 {
 	struct emac_board_info *db = netdev_priv(dev);
-	unsigned long flags;
 	unsigned int reg_val;
 
-	spin_lock_irqsave(&db->lock, flags);
-
 	emac_update_speed(dev);
 	emac_update_duplex(dev);
 
@@ -508,7 +505,15 @@ static void emac_init_device(struct net_device *dev)
 	reg_val = readl(db->membase + EMAC_INT_CTL_REG);
 	reg_val |= (EMAC_INT_CTL_TX_EN | EMAC_INT_CTL_TX_ABRT_EN | EMAC_INT_CTL_RX_EN);
 	writel(reg_val, db->membase + EMAC_INT_CTL_REG);
+}
+
+static void emac_init_device(struct net_device *dev)
+{
+	struct emac_board_info *db = netdev_priv(dev);
+	unsigned long flags;
 
+	spin_lock_irqsave(&db->lock, flags);
+	emac_init_device_no_lock(dev);
 	spin_unlock_irqrestore(&db->lock, flags);
 }
 
@@ -526,7 +531,7 @@ static void emac_timeout(struct net_device *dev, unsigned int txqueue)
 
 	netif_stop_queue(dev);
 	emac_reset(db);
-	emac_init_device(dev);
+	emac_init_device_no_lock(dev);
 	/* We can accept TX packets again */
 	netif_trans_update(dev);
 	netif_wake_queue(dev);
-- 
2.25.1