suse man page for clear_bit

CLEAR_BIT(9)						     Basic C Library Functions						      CLEAR_BIT(9)

NAME
       clear_bit - Clears a bit in memory

SYNOPSIS
       void clear_bit(int nr, volatile unsigned long * addr);

ARGUMENTS
       nr
	   Bit to clear

       addr
	   Address to start counting from

DESCRIPTION
       clear_bit is atomic and may not be reordered. However, it does not contain a memory barrier, so if it is used for locking purposes, you
       should call smp_mb__before_clear_bit and/or smp_mb__after_clear_bit in order to ensure changes are visible on other processors.

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010							      CLEAR_BIT(9)