4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ethan Zhao <ethan.zhao@xxxxxxxxxx>
commit 5ccba44ba118a5000cccc50076b0344632459779 upstream.
System will hang if user set sysctl_sched_time_avg to 0:
[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);
...
}
To fix this issue, check user input value of sysctl_sched_time_avg, keep
it unchanged when hitting invalid input, and set the minimum limit of
sysctl_sched_time_avg to 1 ms.
Reported-by: James Puthukattukaran <james.puthukattukaran@xxxxxxxxxx>
Signed-off-by: Ethan Zhao <ethan.zhao@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: efault@xxxxxx
Cc: ethan.kernel@xxxxxxxxx
Cc: keescook@xxxxxxxxxxxx
Cc: mcgrof@xxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1504504774-18253-1-git-send-email-ethan.zhao@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Steve Muckle <smuckle@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sysctl.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -342,7 +342,8 @@ static struct ctl_table kern_table[] = {
.data = &sysctl_sched_time_avg,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &one,
},
{
.procname = "sched_shares_window_ns",
