Patchwork [v3,2/2,net-next] net: fec: fix spin_lock dead lock

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Submitter Frank Li
Date Feb. 7, 2013, 12:59 a.m.
Message ID <1360198799-25173-2-git-send-email-Frank.Li@freescale.com>
Download mbox | patch
Permalink /patch/218808/
State Accepted
Delegated to: David Miller
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Comments

Frank Li - Feb. 7, 2013, 12:59 a.m.

David Miller - Feb. 8, 2013, 4:37 a.m.
From: Frank Li <Frank.Li@freescale.com>
Date: Thu, 7 Feb 2013 08:59:59 +0800

> =========================================================
> [ INFO: possible irq lock inversion dependency detected ]
> 3.8.0-rc5+ #82 Not tainted
> ---------------------------------------------------------
> swapper/0/0 just changed the state of lock:
>  (&(&fep->hw_lock)->rlock){..-...}, at: [<8034e2f8>] fec_enet_start_xmit+0x48/0x                      2cc
> but this lock took another, SOFTIRQ-unsafe lock in the past:
> (prepare_lock){+.+.+.}
> 
> and interrupts could create inverse lock ordering between them.
> other info that might help us debug this:
> Possible interrupt unsafe locking scenario:
> 
> CPU0				CPU1
> ----				----
> lock(prepare_lock);
> 				local_irq_disable()
> 				lock(&(&fep->hw_lock)->rlock);
> 				lock(prepare_lock);
> <Interrupt>
> lock(&(&fep->hw_lock)->rlock);
> 
> *** DEADLOCK ***
> 
> Signed-off-by: Frank Li <Frank.Li@freescale.com>

Applied.
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Patch

=========================================================
[ INFO: possible irq lock inversion dependency detected ]
3.8.0-rc5+ #82 Not tainted
---------------------------------------------------------
swapper/0/0 just changed the state of lock:
 (&(&fep->hw_lock)->rlock){..-...}, at: [<8034e2f8>] fec_enet_start_xmit+0x48/0x                      2cc
but this lock took another, SOFTIRQ-unsafe lock in the past:
(prepare_lock){+.+.+.}

and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Possible interrupt unsafe locking scenario:

CPU0				CPU1
----				----
lock(prepare_lock);
				local_irq_disable()
				lock(&(&fep->hw_lock)->rlock);
				lock(prepare_lock);
<Interrupt>
lock(&(&fep->hw_lock)->rlock);

*** DEADLOCK ***

Signed-off-by: Frank Li <Frank.Li@freescale.com>
---
No change from v1 to v3. 

 drivers/net/ethernet/freescale/fec_ptp.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index c40526c..1f17ca0 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -104,7 +104,7 @@  void fec_ptp_start_cyclecounter(struct net_device *ndev)
 	unsigned long flags;
 	int inc;
 
-	inc = 1000000000 / clk_get_rate(fep->clk_ptp);
+	inc = 1000000000 / fep->cycle_speed;
 
 	/* grab the ptp lock */
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
@@ -363,6 +363,8 @@  void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev)
 	fep->ptp_caps.settime = fec_ptp_settime;
 	fep->ptp_caps.enable = fec_ptp_enable;
 
+	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
+
 	spin_lock_init(&fep->tmreg_lock);
 
 	fec_ptp_start_cyclecounter(ndev);