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net: fec: fix spin_lock dead lock 

=========================================================
[ 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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Frank Li 2013-02-06 14:59:59 +00:00 committed by David S. Miller
parent 365cc17464
commit 85bd1798b2
1 changed files with 3 additions and 1 deletions
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4
drivers/net/ethernet/freescale/fec_ptp.c
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@ -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);