execute a function after a specified length of time
toid_t itimeout(void (*fn)(), void *arg, long ticks, pl_t pl);
itimeout causes the function specified by fn to be
called after the time interval specified by ticks,
at the interrupt priority level specified by pl.
arg will be passed as the only argument to function fn.
The itimeout call returns immediately
without waiting for the specified function to execute.
Function to execute when the time increment expires.
The function specified by fn runs in interrupt
context in HDK Technical Reference
and must not lower the interrupt priority
below that specified by the pl argument."
fn will be run at some point
after the time interval expires.
Like a device interrupt (see
it may need to be deferred
until the interrupt priority is dropped
to a sufficiently low level.
Timer callback functions are only run
when the interrupt priority level is plbase;
they never interrupt device interrupt handlers.
Argument to the function.
Number of clock ticks to wait before the function is called.
The length of time before the function is called
is not guaranteed to be exactly equal to the requested time,
but will be at least ticks-1 clock ticks in length.
A ticks argument of 0 has the same effect as
a ticks argument of 1.
Both will result in an approximate wait of between 0 and 1 tick
The flag TO_PERIODIC can be logically OR'ed into the
ticks argument to indicate a repeating periodic timer.
When this is used, the specified function will be called
every ticks clock ticks, instead of just once;
successive calls will compensate for any delay in a previous
cycle, so that there is no cumulative drift.
The repeating timer can be canceled by
just like any other timeout.
The interrupt priority level at which the function will be called.
pl must specify a priority level
greater than or equal to ``pltimeout'';
thus, ``plbase'' cannot be used.
for a list of values for pl.
If the function specified by func is successfully scheduled,
returns a non-zero identifier that can be passed to the
function to cancel the request.
If the function could not be scheduled,
returns a value of 0.
If itimeout is called holding a lock
that is contended for by fn,
the caller must hold the lock at a processor level
greater than the base processor level.
Drivers should be careful to cancel any pending
functions that access data structures
before these structures are de-initialized or deallocated.
Context and synchronization
Non-blockable, user or blockable
for an example of itimeout.
3, 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp
Differences between versions
Starting with DDI version 7,
returns an error instaed of causing a panic
when no more space is available,
so drivers can handle the error,
which improves system reliability and availability.
also allows the driver
to select an interrupt priority other than plhi.
``Timeouts'' in HDK Technical Reference
19 June 2005
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005