Messages in this thread | | | Date | Fri, 23 Feb 2007 14:13:07 -0800 | From | "john stultz" <> | Subject | Re: radeon breaks with clocksource_jiffies |
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Crud, my poor gmail skills dropped lkml on the CC list for this one.
On 2/23/07, john stultz <johnstul@us.ibm.com> wrote: > On 2/23/07, David Miller <davem@davemloft.net> wrote: > > While probeing PLL information via radeon_get_pllinfo(), it does a > > "gettimeofday(); do_something(); gettimeofday();" type sequence > > explicitly with interrupts disabled, so ends up with a zero > > measurement which then results in a bunch of divisions by zero. > > This is at module init time? If so I just sent out a patch yesterday > to akpm that might help this issue (assuming other clocksources are > available on the hardware). > > > > We should decide whether gettimeofday() can be expected to advance with > > interrupts disabled, or that clocksource_jiffies is simply invalid because > > of this behavior. > > Some arches have no fine-grained timekeeping, so I don't think it can > always be assumed, but where hardware is available it should function. > > It should be noted that with older kernels, if interrupts were > disabled right before a tick, it would be possible that > gettimeofday()'s limiting code would cause time to stop advancing > until interrupts were re-enabled. So theoretically its not really a > new issue. > > The timekeeping_is_continuous() function could be used to flag this > sort of "software driven vs continuous" clocksource cases. > > thanks > -john > - 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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