The rwsem API in brief

The rwsem API looks like:

#include <linux/rwsem.h>

void init_rwsem(struct rw_semaphore *sem);

void down_read(struct rw_semaphore *sem);
int down_read_trylock(struct rw_semaphore *sem);  
        /* non-zero = success! */
void up_read(struct rw_semaphore *sem);

void down_write(struct rw_semaphore *sem);
int down_write_trylock(struct rw_semaphore *sem);
void up_write(struct rw_semaphore *sem);

There is no interruptible version