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Linus Torvalds wrote: > On Tue, 17 Jul 2007, Ingo Molnar wrote: > >> * Ian Kent <raven@themaw.net> wrote: >> >>> In several places I have code similar to: >>> >>> wait.tv_sec = time(NULL) + 1; >>> wait.tv_nsec = 0; >>> > > Ok, that definitely should work. > > Does the patch below help? > > Spectacularly no! With this patch the "glitch1" script with multiple scrolling windows has all xterms and glxgears stop totally dead for ~200ms once per second. I didn't properly test anything else after that. Since the automount issue doesn't seem to start until something kicks it off, I didn't see it but that doesn't mean it's fixed. >> ah! It passes in a low-res time source into a high-res time interface >> (pthread_cond_timedwait()). Could you change the time(NULL) + 1 to >> time(NULL) + 2, or change it to: >> >> gettimeofday(&wait, NULL); >> wait.tv_sec++; >> > > This is wrong. It's wrong for two reasons: > > - it really shouldn't be needed. I don't think "time()" has to be > *exactly* in sync, but I don't think it can be off by a third of a > second or whatever (as the "30% CPU load" would seem to imply) > > - gettimeofday works on a timeval, pthread_cond_timedwait() works on a > timespec. > > So if it actually makes a difference, it makes a difference for the > *wrong* reason: the time is still totally nonsensical in the tv_nsec field > (because it actually got filled in with msecs!), but now the tv_sec field > is in sync, so it hides the bug. > > Anyway, hopefully the patch below might help. But we probably should make > this whole thing a much more generic routine (ie we have our internal > "getnstimeofday()" that still is missing the second-overflow logic, and > that is quite possibly the one that triggers the "30% off" behaviour). > > Hope that info helps. > Ingo, I'd suggest: > - ger rid of "timespec_add_ns()", or at least make it return a return > value for when it overflows. > - make all the people who overflow into tv_sec call a "fix_up_seconds()" > thing that does the xtime overflow handling. > > Linus > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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