Mastering Linux Kernel Development

Operation interfaces:

Wait/wound mutexes are represented through struct ww_mutex defined in the header <linux/ww_mutex.h>:

struct ww_mutex {
       struct mutex base;
       struct ww_acquire_ctx *ctx;
# ifdef CONFIG_DEBUG_MUTEXES
       struct ww_class *ww_class;
#endif
};

The first step to use wait/wound mutex is to define a class, which is a mechanism to represent a group of locks. When concurrent tasks contend for the same locks, they must do so by specifying this class.

A class can be defined using a macro:

static DEFINE_WW_CLASS(bufclass);

Each class declared is an instance of type struct ww_class and contains an atomic counter stamp, which is used to hold a sequence number that records which one of the contending tasks got there first. Other fields are ...