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 (lockval.tickets.next != lockval.tickets.owner) { wfe(); lockval.tickets.owner = 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:- arch_spin_lock _raw_spin_lock vprintk_emit ----> raw_spin_lock(&logbuf_lock); vprintk_default printk smp_init 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