wake_up_bit(9) centos man page | unix.com

WAKE_UP_BIT(9)							   Driver Basics						    WAKE_UP_BIT(9)

NAME
       wake_up_bit - wake up a waiter on a bit

SYNOPSIS
       void wake_up_bit(void * word, int bit);

ARGUMENTS
       word
	   the word being waited on, a kernel virtual address

       bit
	   the bit of the word being waited on

DESCRIPTION
       There is a standard hashed waitqueue table for generic use. This is the part of the hashtable's accessor API that wakes up waiters on a
       bit. For instance, if one were to have waiters on a bitflag, one would call wake_up_bit after clearing the bit.

       In order for this to function properly, as it uses waitqueue_active internally, some kind of memory barrier must be done prior to calling
       this. Typically, this will be smp_mb__after_clear_bit, but in some cases where bitflags are manipulated non-atomically under a lock, one
       may need to use a less regular barrier, such fs/inode.c's smp_mb, because spin_unlock does not guarantee a memory barrier.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							    WAKE_UP_BIT(9)