Kernel gets deadlocked during smp booting

AYAN KUMAR HALDER ayankumarh at
Tue Jun 16 07:24:28 EDT 2015

Hi All,

I am booting kernel 4.0.4 on an ARM based custom SOC with SMP enabled.
I see that the kernel gets deadlocked on a spinlock. To be precise,

static inline void arch_spin_lock(arch_spinlock_t *lock)
// loops in the following while loop for indefinite period
while ( != {
        wfe(); = ACCESS_ONCE(lock->tickets.owner);


Can someone explain to me what does the loop exactly do.
Besides, any pointers about how to debug such issues.

The backtrace shows the following:-
vprintk_emit ----> raw_spin_lock(&logbuf_lock);

I can guess that the deadlock is being caused due to logbuf_lock. But,
I am unable to proceed further.

Thanks and Regards,
Ayan kumar Halder

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