Messages in this thread Patch in this message | | | From | Ethan Zhao <> | Subject | [PATCH] sched: reset sysctl_sched_time_avg to default when | Date | Fri, 1 Sep 2017 19:31:54 +0800 |
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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; + return (u64)sysctl_sched_time_avg * NSEC_PER_MSEC / 2; } -- 1.8.3.1
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