Messages in this thread | | | From | Ethan Zhao <> | Date | Sat, 2 Sep 2017 08:33:03 +0800 | Subject | Re: [PATCH] sched: reset sysctl_sched_time_avg to default when |
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Yep, that is the first place I considered to set the limit, but that would break KABI ?
Thanks, Ethan
On Fri, Sep 1, 2017 at 8:32 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Fri, Sep 01, 2017 at 07:31:54PM +0800, Ethan Zhao wrote: >> System will hang if user set sysctl_sched_time_avg to 0 by >> >> [root@XXX ~]# sysctl kernel.sched_time_avg_ms=0 >> >> Stack traceback for pid 0 >> 0xffff883f6406c600 0 0 1 3 R 0xffff883f6406cf50 *swapper/3 >> ffff883f7ccc3ae8 0000000000000018 ffffffff810c4dd0 0000000000000000 >> 0000000000017800 ffff883f7ccc3d78 0000000000000003 ffff883f7ccc3bf8 >> ffffffff810c4fc9 ffff883f7ccc3c08 00000000810c5043 ffff883f7ccc3c08 >> Call Trace: >> <IRQ> [<ffffffff810c4dd0>] ? update_group_capacity+0x110/0x200 >> [<ffffffff810c4fc9>] ? update_sd_lb_stats+0x109/0x600 >> [<ffffffff810c5507>] ? find_busiest_group+0x47/0x530 >> [<ffffffff810c5b84>] ? load_balance+0x194/0x900 >> [<ffffffff810ad5ca>] ? update_rq_clock.part.83+0x1a/0xe0 >> [<ffffffff810c6d42>] ? rebalance_domains+0x152/0x290 >> [<ffffffff810c6f5c>] ? run_rebalance_domains+0xdc/0x1d0 >> [<ffffffff8108a75b>] ? __do_softirq+0xfb/0x320 >> [<ffffffff8108ac85>] ? irq_exit+0x125/0x130 >> [<ffffffff810b3a17>] ? scheduler_ipi+0x97/0x160 >> [<ffffffff81052709>] ? smp_reschedule_interrupt+0x29/0x30 >> [<ffffffff8173a1be>] ? reschedule_interrupt+0x6e/0x80 >> <EOI> [<ffffffff815bc83c>] ? cpuidle_enter_state+0xcc/0x230 >> [<ffffffff815bc80c>] ? cpuidle_enter_state+0x9c/0x230 >> [<ffffffff815bc9d7>] ? cpuidle_enter+0x17/0x20 >> [<ffffffff810cd6dc>] ? cpu_startup_entry+0x38c/0x420 >> [<ffffffff81053373>] ? start_secondary+0x173/0x1e0 >> >> Because divide-by-zero error happens in function >> >> update_group_capacity() >> update_cpu_capacity() >> scale_rt_capacity() >> { >> ... >> total = sched_avg_period() + delta; >> used = div_u64(avg, total); >> ... >> } >> >> Seems this issue could be reproduced on all I tried stable 4.1 - last >> kernel. >> >> To fix this issue, reset sysctl_sched_time_avg to default value >> MSEC_PER_SEC if user input invalid value in function >> >> sched_avg_period() >> >> Reported-by: James Puthukattukaran <james.puthukattukaran@oracle.com> >> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com> >> --- >> Tested on stable 4.1, compiled on stable 4.13-rc5 >> kernel/sched/sched.h | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> index eeef1a3..b398560 100644 >> --- a/kernel/sched/sched.h >> +++ b/kernel/sched/sched.h >> @@ -1620,6 +1620,9 @@ static inline void rq_last_tick_reset(struct rq *rq) >> >> static inline u64 sched_avg_period(void) >> { >> + if (unlikely(sysctl_sched_time_avg <= 0)) >> + sysctl_sched_time_avg = MSEC_PER_SEC; >> + > > Sight, no.. you can set limits in the sysctl table.
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