alignment requirements for kmutex_t

Hello,
I found that global variable of type kmutex_t is on many places defined 
like:
kmutex_t variable_name __cacheline_aligned;

Two questions,
1. Is __cacheline_aligned mandatory for global/static variables of type 
kmutex in kernel space ?
2. Regarding to alignment what are requirements for kmutex placed in 
kernel dynamically allocated memory ?

Peter