MOD_INC_USE_COUNT

Section: Kernel Functions (9)
Updated: $Date:$
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NAME

MOD_INC_USE_COUNT, MOD_DEC_USE_COUNT - Support reference counting of modules

SYNOPSIS

#include <linux/module.h>

#define MOD_INC_USE_COUNT
#define MOD_DEC_USE_COUNT

DESCRIPTION

These macros support reference counting of modules during their lifetime. Each time MOD_INC_USE_COUNT(9) is invoked, the kernel increases the number of counted references to the module. The MOD_DEC_USE_COUNT(9) decreases the reference count.

The reference count is used by the kernel to know when a module is no longer in use by the device or application software. A MOD_INC_USE_COUNT(9) is generally placed in the open entry for a driver, and a MOD_DEC_USE_COUNT(9) in the release for the driver, to count the number of times the device has been opened, and thus prevent the module being unloaded when in use. The device driver may increment the use count other times, such as when memory is mapped or the module must remain loaded for external events.

If the device driver is not compiled as a module (MODULE is not defined) then the macro reduces to no behavior.

RETURN VALUE

These macros take no parameters and return no result.

AVAILABILITY

Linux 1.0+

AUTHOR

Stephen Williams <steve@icarus.com>