nanospin_count()
QNX SDP8.0C Library ReferenceAPIDeveloper
Busy-wait without blocking for a number of iterations
Synopsis:
#include <time.h>
void nanospin_count( unsigned long count );
Arguments:
- count
- The number of iterations that you want to busy-wait for.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The nanospin_count() function busy-waits for the number of iterations specified in count. Use nanospin_ns_to_count() to turn a number of nanoseconds into an iteration count suitable for nanospin_count().
Note:
The nanospin*() functions are designed for use with
hardware that requires short time delays between accesses.
You should use them to delay only for times less than a few milliseconds.
For longer delays, use the POSIX
timer_*()
functions.
Examples:
Busy-wait for at least 100 nanoseconds:
#include <time.h>
#include <sys/syspage.h>
unsigned long time = 100;
…
/* Wake up the hardware, then wait for it to be ready. */
const unsigned long count = nanospin_ns_to_count( time );
if ( count != -1UL ) {
nanospin_count( count );
} else {
/* Check errno and handle error here somehow */
}
/* Use the hardware. */
…
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
Caveats:
You should use busy-waiting only when absolutely necessary for accessing hardware.
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