Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "We can lock/unlock the spinlock using the spin_lock() and spin_unlock() inline functions, both defined in include/linux/spinlock.h."

A block of code is set as follows:

struct mutex {
    atomic_long_t owner;
    spinlock_t wait_lock;
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
    struct optimistic_spin_queue osq; /* Spinner MCS lock */

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

struct fake_data {
    struct i2c_client *client;
    u16 reg_conf;
    struct mutex mutex;
};

Any command-line input or output is written as follows:

[342081.385491] Wait queue example
[342081.385505] Going to sleep my_init
[342081.385515] Waitqueue module handler work_handler
[342086.387017] Wake up the sleeping module

Tips or Important Notes

Appear like this.