Messages in this thread | | | Date | Fri, 22 Nov 2013 13:07:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [tip:sched/urgent] sched: Check sched_domain before computing group power |
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On Thu, Nov 21, 2013 at 09:22:24AM -0800, Yinghai Lu wrote: > On Thu, Nov 21, 2013 at 7:03 AM, Peter Zijlstra <peterz@infradead.org> wrote: > >> > >> This one seems fix NULL reference in compute_group_power. > >> > >> but get following on current Linus tree plus tip/sched/urgent. > >> > >> divide error: 0000 [#1] SMP > >> [ 28.190477] Modules linked in: > >> [ 28.192012] CPU: 11 PID: 484 Comm: kworker/u324:0 Not tainted > >> 3.12.0-yh-10487-g4b94e59-dirty #2044 > >> [ 28.210488] Hardware name: Oracle Corporation Sun Fire > >> [ 28.229877] task: ffff88ff25205140 ti: ffff88ff2520a000 task.ti: > >> ffff88ff2520a000 > >> [ 28.236139] RIP: 0010:[<ffffffff810d9ff4>] [<ffffffff810d9ff4>] > >> find_busiest_group+0x2b4/0x8a0 > > > > Hurmph.. what kind of hardware is that? and is there anything funny you > > do to make it do this? > > intel nehanem-ex or westmere-ex 8 sockets system. > > I tried without my local patches, the problem is still there.
And I suppose a kernel before
863bffc80898 ("sched/fair: Fix group power_orig computation")
work fine, eh?
I'll further assume that your RIP points to:
sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
indicating that sds.total_pwr := 0.
update_sd_lb_stats() computes it like:
sds->total_pwr += sgs->group_power;
which comes out of update_sg_lb_stats() like:
sgs->group_power = group->sgp->power;
Which we compute in update_group_power() similarly to how we did before 863bffc80898.
Which leaves me a bit puzzled.
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