BUG: spinlock lockup

From: naveen yadav
Date: Sat Jan 18 2014 - 02:26:07 EST

Dear All,

We are using 3.8.x kernel on ARM, We are facing soft lockup issue.
Following are the logs.

BUG: spinlock lockup suspected on CPU#0, process1/525
lock: 0xd8ac9a64, .magic: dead4ead, .owner: <none>/-1, .owner_cpu: -1

1 . Looks like lock is available as owner is -1, why arch_spin_trylock
is getting failed ?

2. There is a patch : ARM: spinlock: retry trylock operation if strex
fails on free lock
In this patch, A loop has been added around strexeq %2, %0, [%3]".
{Comment "retry the trylock operation if the lock appears
to be free but the strex reported failure"}

but arch_spin_trylock is called by __spin_lock_debug and its already
getting called in loops. So what purpose is resolves?

static void __spin_lock_debug(raw_spinlock_t *lock)
u64 i;
u64 loops = loops_per_jiffy * HZ;

for (i = 0; i < loops; i++) {
if (arch_spin_trylock(&lock->raw_lock))
/* lockup suspected: */
spin_dump(lock, "lockup suspected");

3. Is this patch useful to us, How can we reproduce this scenario ?
Scenario : Lock is available but arch_spin_trylock is returning as failure

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