mutex_lock() / mutex_unlock()

Purpose

Protects shared state in process context where sleeping is allowed.

Header

#include <linux/mutex.h>

Prototype

void mutex_lock(struct mutex *lock);
void mutex_unlock(struct mutex *lock);

Parameters

• lock: pointer to an initialized struct mutex.

Return Value

• mutex_lock() returns no value and may sleep.
• mutex_unlock() releases the mutex.

Minimal Example

mutex_lock(&dev->lock);
/* update shared state */
mutex_unlock(&dev->lock);

Common Pitfalls

• Do not use mutexes in hard IRQ context.
• Avoid holding mutexes while copying large data to/from user space.
• Use clear ownership rules to prevent deadlocks.

Related Topics

• Kernel Driver