Similar to what we did with our mutex locking sample driver (the Mutex locking – an example driver section), to illustrate the simple usage of a spinlock, we shall make a copy of our earlier ch12/1_miscdrv_rdwr_mutexlock driver as a starting template and then place it in a new kernel driver; that is, ch12/2_miscdrv_rdwr_spinlock. Again, here, we'll only show small parts of the diff (the differences, the delta generated by diff(1)) between that program and this one (we won't show every line of the diff, only the relevant portions):
// location: ch12/2_miscdrv_rdwr_spinlock/
+#include <linux/spinlock.h>
[ ... ]
-#define OURMODNAME "miscdrv_rdwr_mutexlock"
+#define OURMODNAME "miscdrv_rdwr_spinlock"
[ ... ]
static int ga, gb = 1;
-DEFINE_MUTEX(lock1); // this mutex lock is meant to protect the integers ga and gb
+DEFINE_SPINLOCK(lock1); // this spinlock protects the global integers ga and...
