11-13-2015
Since you are in kernel mode context you most likely need a spinlock. What you have is called a critical section.
5.5. Spinlocks discusses spinlocks in general.
http://tuxthink.blogspot.com/2013/06...x-example.html
Since you asked this question I would recommend lots of reading on your own. FIRST. It is easy to crash or hang the system with slightly less than perfect code. Debugging kernel code can be painful, some debugging tools may still require using two physically separate computers.
It is easier to do your homework first. Write dirt simple code for practice, first.
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LEARN ABOUT OSF1
lock_write
lock_write(9r) lock_write(9r)
NAME
lock_write - Asserts a complex lock with write access
SYNOPSIS
#include <kern/lock.h>
void lock_write(
lock_t lock_structptr );
ARGUMENTS
Specifies a pointer to the complex lock structure, lock. This is the lock structure associated with the resource on which you want to
assert a complex lock with write access. The lock structure is an opaque data structure; that is, its associated members are referenced and
manipulated by the operating system and not by the user of the complex lock mechanism.
DESCRIPTION
The lock_write routine asserts a lock with exclusive write access for the resource associated with the specified lock structure pointer.
This means that once a write lock is asserted, no other kernel thread can gain read or write access to the resource until it is released.
To release a complex write lock successfully asserted by lock_write, call the lock_done routine.
NOTES
You must call lock_init (once only) prior to calling lock_write to initialize the lock structure pointer for the resource. A resource,
from the kernel module's standpoint, is data that more than one kernel thread can manipulate. You can store the resource in global vari-
ables and in data structure members.
RETURN VALUES
None
FILES
SEE ALSO
Routines: lock_done(9r), lock_read(9r), lock_terminate(9r), lock_try_read(9r), lock_try_write(9r)
Data Structures: lock(9s)
lock_write(9r)