NetBSD 6.1.5 - man page for delay (netbsd section 9)

DELAY(9)			  BSD Kernel Developer's Manual 			 DELAY(9)

NAME
     delay, DELAY -- microsecond delay

SYNOPSIS
     #include <machine/param.h>

     void
     delay(unsigned int us);

     void
     DELAY(unsigned int us);

DESCRIPTION
     Wait approximately us microseconds.

     The delay is implemented as a machine loop, preventing events other than interrupt handlers
     for unmasked interrupts to run.  DELAY() is reentrant (doesn't modify any global kernel or
     machine state) and is safe to use in interrupt or process context.

     For long delays, condition variables should be considered, however they can only be used
     from process context and their resolution is limited by the system clock frequency.

SEE ALSO
     condvar(9), hz(9), kpause(9)

BSD					  July 20, 2011 				      BSD