Messages in this thread | | | Date | Sun, 6 Dec 2015 12:56:03 -0800 | From | "Paul E. McKenney" <> | Subject | Re: Possible issue with commit 4961b6e11825? |
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On Sat, Dec 05, 2015 at 11:01:24AM -0800, Paul E. McKenney wrote: > On Fri, Dec 04, 2015 at 03:20:22PM -0800, Paul E. McKenney wrote: > > Hello! > > > > Are there any known issues with commit 4961b6e11825 (sched: core: Use > > hrtimer_start[_expires]())? > > > > The reason that I ask is that I am about 90% sure that an rcutorture > > failure bisects to that commit. I will be running more tests on > > 3497d206c4d9 (perf: core: Use hrtimer_start()), which is the predecessor > > of 4961b6e11825, and which, unlike 4961b6e11825, passes a 12-hour > > rcutorture test with scenario TREE03. In contrast, 4961b6e11825 gets > > 131 RCU CPU stall warnings, 132 reports of one of RCU's grace-period > > kthreads being starved, and 525 reports of one of rcutorture's kthreads > > being starved. Most of the test runs hang on shutdown, which is no > > surprise if an RCU CPU stall is happening at about that time. > > > > But perhaps 3497d206c4d9 was just getting lucky, hence additional testing > > over the weekend. > > And it was getting lucky. In a set of 24 two-hour runs (triple parallel) > on an earlier commit (not 3497d206c4d9, no clue what I was thinking) got > me two failed runs, for a total of 49 reports of one of RCU's grace-period > kthreads being starved, no reports of rcutorture's kthreads being starved, > and no hangs on shutdown. So much lower failure rate, but still failures. > > At this point, I am a bit disgusted with bisection, so my next test cycle > (36 two-hour runs on a system capable of doing three concurrently) is on > the most recent -rcu, but with CPU hotplug disabled. If that shows failures, > then I hammer 3497d206c4d9 hard.
And no failures on current -rcu with CPU hotplug disabled. So this seems to be specific to CPU hotplug. So my next step is to fix some remaining known CPU-hotplug issues in RCU.
And Thomas, when you get those CPU-hotplug patches ready, I have a testcase for you! ;-)
Thanx, Paul
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