wakeup(9r)wakeup(9r)NAMEwakeup - General: Wakes up all processes sleeping on a specified
address
SYNOPSIS
void wakeup(
caddr_t channel );
ARGUMENTS
Specifies the address on which the wakeup is to be issued.
DESCRIPTION
The wakeup routine wakes up all processes sleeping on the address spec‐
ified by the channel argument. All processes sleeping on this address
are awakened and made ready to be scheduled according to the priorities
they specified when they went to sleep. It is possible that there are
no processes sleeping on the channel at the time the wakeup is issued.
This situation can occur for a variety of reasons and does not repre‐
sent an error condition.
The sleep and wakeup routines block and unblock a process. Generally, a
device driver issues these routines on behalf of a process requesting
I/O while a transfer is in progress. That is, a process requesting I/O
is put to sleep on an address associated with the request by the appro‐
priate device driver routine. When the transfer has asynchronously com‐
pleted, the device driver interrupt service routine issues a wakeup on
the address associated with the completed request. This action makes
the relevant process to be scheduled.
The process resumes execution within the relevant device driver routine
at the point immediately following the request to sleep. The driver, on
behalf of the process, can then determine whether the condition for
which it was sleeping (in this example, completion of an I/O request)
has been removed. If so, it can continue on to complete the I/O
request. Otherwise, the appropriate driver routine can decide to put
the process back to sleep to await removal of the indicated condition.
RETURN VALUES
None
SEE ALSO
Routines: mpsleep(9r), sleep(9r)wakeup(9r)
