Typically, you can find very insightful comments within the kernel source tree. Here's a great one that neatly summarizes the rules you must follow to correctly use a mutex lock; please read this carefully:
// include/linux/mutex.h
/*
* Simple, straightforward mutexes with strict semantics:
*
* - only one task can hold the mutex at a time
* - only the owner can unlock the mutex
* - multiple unlocks are not permitted
* - recursive locking is not permitted
* - a mutex object must be initialized via the API
* - a mutex object must not be initialized via memset or copying
* - task may not exit with mutex held
* - memory areas where held locks reside must not be freed
* - held mutexes must not be reinitialized
* - mutexes may not be used in hardware or software interrupt
* contexts such as tasklets and timers
*
* These semantics are fully enforced when DEBUG_MUTEXES is
* enabled. Furthermore, besides enforcing the above rules, the mutex
* [ ......