DESCRIPTION

     The sleep_on function provides  a  means  for  synchronizing
     between processes and with interrupt handlers. The condition
     parameter is a pointer to a pointer to the opaque wait_queue
     type. Initialize the condition variable to zero, then pass a
     pointer to it to the sleep_on function. The basic idea is as
     follows:

     struct wait_queue*con = 0;
          [...]
     sleep_on(&con);

     While a process is sleeping, it is fully  interruptible,  no
     matter  what  the  cpu state when entering the function. The
     cpu state is restored on being awakened.

     If a null(0) is passed to sleep_on, it returns  immediately,
     without sleeping. This is a no-op.

RETURN VALUE

     The sleep_on function only returns when explicitly awakened.

AVAILABILITY

     Linux 1+

SEE ALSO

     wake_up(9)

     /usr/src/linux/kernel/sched.c

AUTHOR

     Stephen Williams <steve@icarus.com>

BUGS

     A call to sleep_on(0) seems like an interesting way to  test
     for  and  momentarily allow interrupts, but that is not what
     happens.

     The  sleep_on  function  cannot  be  called   by   interrupt
     handlers.

     The function is not atomic with the condition tests that the
     driver  writer  might  include,  so  the  code executing the
     sleep_on function is protected from interrupts.  Failure  to
     do so generally leads to race