If ( sigwait( &lAlarm, &lReceivedSignal ) != 0 )Įrror( EXIT_FAILURE, errno, "Failed to wait for next clock tick" ) Ĭlock_gettime( CLOCK_REALTIME, &lCurrentTime ) If ( setitimer( ITIMER_REAL, &lTimer, NULL ) != 0 )Įrror( EXIT_FAILURE, errno, "Could not start interval timer" ) Ĭlock_gettime( CLOCK_REALTIME, &lLastTime ) Block alarm signal, will be waited on explicitly #define TIMESPEC_TO_NS( aTime ) ( ( NS_PER_SECOND * ( ( long long int ) _sec ) ) \ Compile with -lrt and run with sudo chrt -f 50 #include On others, it will print out batches of warning that it slept 10+ milliseconds over the target time. On some systems it will only print out one warning that's it slept about 100 microseconds or so over the target time. Here's a test program using itimer for interrupts. But I'm seeing some systems sleep way longer (10+ milliseconds) than they should using an itimer. That is, since the hpet can't interrupt at exactly the frequency I want, the interrupts start to drift from wall time. And on some systems, the itimer provides periodic interrupts that are more stable over time.
#Itimer linux driver
It would be nicer to use the itimer interface provided by Linux instead of interfacing with the hardware device driver directly. For example, on a Core 2 Quad, the example program included in the kernel documentation fails at HPET_IE_ON when set to poll. But I can't get it working on some machines that have hpet available as a clocksource either. Obviously I can't use it on machines that don't actually have a HPET. I'd like to sleep 1 millisecond or 250 microseconds between interrupts.Įnabling periodic interrupts from /dev/hpet works pretty well, but it doesn't seem to work on some machines.
I want to be interrupted at frequencies that are powers of ten, so enabling interrupts from /dev/rtc isn't ideal. Original Standard can be obtained online at. Standard, the original IEEE and The Open Group Standard is the referee document. In theĮvent of any discrepancy between this version and the original IEEE and The Open Group The Institute of Electrical and Electronics Engineers, Inc and The Open Group. Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
#Itimer linux portable
Portions of this text are reprinted and reproduced in electronic form from IEEE Stdġ003.1, 2003 Edition, Standard for Information Technology - Portable Operating System Getitimer(), gettimeofday(), select(), setitimer() SEE ALSO, , the System Interfaces volume of IEEE Std 1003.1-2001, Inclusion of the header may make visible all symbols from the Int getitimer(int, struct itimerval *) int gettimeofday(struct timeval *restrict, void *restrict) int select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict, struct timeval *restrict) int setitimer(int, const struct itimerval *restrict, struct itimerval *restrict) int utimes(const char *, const struct timeval ) (LEGACY ) The following shall be declared as functions and may also be defined as macros. The following shall be defined as described in : FD_CLR() FD_ISSET() The header shall define the following values for the which argument ofĭecrements both in process virtual time and when the system is running on behalf of The fd_set type shall be defined as described in. The time_t and suseconds_t types shall be defined as described in. Struct timeval it_interval Timer interval. The header shall define the itimerval structure that includes at least the The header shall define the timeval structure that includes at least the Provided by: manpages-posix-dev_2.16-1_all
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