Re: [Vm-dev] Tasks of the heartbeat code

On 25 Dec 2015, at 21:40, Holger Freyther holger@freyther.de wrote:

Dear Eliot,

I was thinking what to do to make the below race free? I think I will:

* Block the SIGIO * Memory barrier? * Check if an event is already queued and then restore mask and return * Set itimer * sigsuspend * Unblock SIGIO * dispatch

Does this look correct? At the same time I think the per display backend relinquish code can be replaced with a generic unix one? Maybe even separating waiting for a timeout and waiting for I/O could be done and creates a better internal interface?

kind regards holger

static sqInt display_ioRelinquishProcessorForMicroseconds(sqInt microSeconds) {

• aioSleepForUsecs(handleEvents() ? 0 : microSeconds);

• sigset_t set;
• sigemptyset(&set);
• extern usqLong getNextWakeupUsecs();
• if (getNextWakeupUsecs() == 0) {
• sigsuspend(&set);
• } else {
• usqLong nextWakeUp = getNextWakeupUsecs();
• usqLong now = ioUTCMicroseconds();
• struct itimerval value;
• sqLong deltaMicro = nextWakeUp - now;
• if (deltaMicro < 1)

• deltaMicro = 1;
  

• /* don't re-run automatically */
• value.it_interval.tv_sec = value.it_interval.tv_usec = 0;
• value.it_value.tv_sec = deltaMicro / 1000000;
• value.it_value.tv_usec = deltaMicro % 1000000;
• setitimer(ITIMER_REAL, &value, &value);
• sigsuspend(&set);
• value.it_value = value.it_interval;
• setitimer(ITIMER_REAL, &value, NULL);
• extern int doDispatch;
• if (doDispatch) {

• doDispatch = 0;
  

• aioPoll(0);
  

• }
• }