Barry Song <21cn...@gmail.com> writes: > 2012/7/18 Colin Cross <ccr...@android.com>: >> Many clocks that are used to provide sched_clock will reset during >> suspend. If read_sched_clock returns 0 after suspend, sched_clock will >> appear to jump forward. This patch resets cd.epoch_cyc to the current >> value of read_sched_clock during resume, which causes sched_clock() just >> after suspend to return the same value as sched_clock() just before >> suspend. >> >> In addition, during the window where epoch_ns has been updated before >> suspend, but epoch_cyc has not been updated after suspend, it is unknown >> whether the clock has reset or not, and sched_clock() could return a >> bogus value. Add a suspended flag, and return the pre-suspend epoch_ns >> value during this period. > > Acked-by: Barry Song <21cn...@gmail.com> > > this patch should also fix the issue that: > 1. launch some rt threads, rt threads sleep before suspend > 2. repeat to suspend/resume > 3. after resuming, waking up rt threads > > repeat 1-3 again and again, sometimes all rt threads will hang after > resuming due to wrong sched_clock will make sched_rt think rt_time is > much more than rt_runtime (default 950ms in 1s). then rt threads will > lost cpu timeslot to run since the 95% threshold is there.
Re-visiting this in light of a related problem. I've run into a similar issue where IRQ threads are prevented from running during resume becase the RT throttling kicks because RT runtime is accumulated during suspend. Using the 'needs_suspend' version fixes this problem too. However, because of the RT throttling issue, it seems like *all* platforms should be using the 'needs_suspend' version always. But, as already pointed out, that makes the timed printk output during suspend/resume rather unhelpful. Having to choose between useful printk times during suspend/resume and functioning IRQ threads during suspend/resume isn't a choice I want to make. I'd rather have both. Any ideas? Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
