ARM build fails with the following symptom: CC arch/arm/kernel/asm-offsets.s In file included from include/linux/seqlock.h:29, from include/linux/time.h:8, from include/linux/timex.h:56, from include/linux/sched.h:57, from arch/arm/kernel/asm-offsets.c:13: include/linux/spinlock.h: In function 'spin_unlock_wait': include/linux/spinlock.h:360: error: implicit declaration of function 'cpu_relax' make[1]: *** [arch/arm/kernel/asm-offsets.s] Error 1 Fix it by including <asm/processor.h>. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>