drv_usecwait(D3)drv_usecwait(D3)NAMEdrv_usecwait - busy-wait for specified interval
SYNOPSIS
#include <sys/types.h>
#include <sys/ddi.h>
void drv_usecwait(clock_t microsecs);
Arguments
microsecs The number of microseconds to busy-wait.
DESCRIPTIONdrv_usecwait causes the caller to busy-wait for at least the number of
microseconds specified by microsecs. The amount of time spent busy-
waiting may be greater than the time specified by microsecs but will not
be less.
Return Values
None
USAGEdrv_usecwait should only be used to wait for short periods of time (less
than a clock tick) or when it is necessary to wait without sleeping (for
example, at interrupt level). When the desired delay is at least as long
as clock tick and it is possible to sleep, the delay(D3) function should
be used instead since it will not waste processor time busy-waiting as
drv_usecwait does.
Because excessive busy-waiting is wasteful the driver should only make
calls to drv_usecwait as needed, and only for as much time as needed.
drv_usecwait does not raise the interrupt priority level; if the driver
wishes to block interrupts for the duration of the wait, it is the
driver's responsibility to set the priority level before the call and
restore it to its original value afterward.
Level
Initialization, Base or Interrupt.
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks may be held
across calls to this function.
Warnings
Busy-waiting can increase the preemption latency experienced by high
priority processes. Since short and bounded preemption latency can be
critical in a real time environment, drivers intended for use in such an
environment should not use this interface or should limit the length of
the wait to an appropriately short length of time.
Page 1
drv_usecwait(D3)drv_usecwait(D3)REFERENCESdelay(D3), drv_hztousec(D3), drv_usectohz(D3), itimeout(D3),
untimeout(D3)
Page 2
