On 2016/7/1 16:23, Eric Dumazet wrote: > On Fri, 2016-07-01 at 16:10 +0800, Ding Tianhong wrote: >> On 2016/7/1 15:57, Eric Dumazet wrote: >>> On Fri, 2016-07-01 at 15:38 +0800, Ding Tianhong wrote: >>> ... >>>> net/ipv6/addrconf.c | 6 ++++++ >>>> 1 file changed, 6 insertions(+) >>>> >>>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c >>>> index f555f4f..e294a3d 100644 >>>> --- a/net/ipv6/addrconf.c >>>> +++ b/net/ipv6/addrconf.c >>>> @@ -3284,6 +3284,12 @@ restart: >>>> spin_unlock_bh(&addrconf_hash_lock); >>>> } >>>> >>>> + /* >>>> + * It is safe here to schedule out to avoid softlocking if preempt >>>> + * is disabled. >>>> + */ >>>> + cond_resched(); >>>> + >>>> write_lock_bh(&idev->lock); >>>> >>>> addrconf_del_rs_timer(idev); >>> >>> Seeing you apparently cooked your patch against an old kernel (which >>> one ?) ... >>> >>> I tried vanilla net-next kernel, and apparently I could not trigger the >>> softlockup you mentioned. >>> >>> Are you sure current kernel has a bug to begin with ? >>> >> have you disable the preempt? The problem will disappear if you enable the >> preempt voluntary or preempt. >> CONFIG_PREEMPT_NONE=y >> # CONFIG_PREEMPT_VOLUNTARY is not set >> # CONFIG_PREEMPT is not set >> >> I test the 4.1 lts kernel and found this problem, and I didn't found any >> patch to fix this from linux 4.1, but I will try to test in 4.7 kernel >> version. > > I usually do not have PREEMPT enabled in my kernels. > > $ grep PREEMPT .config > CONFIG_PREEMPT_NOTIFIERS=y > CONFIG_PREEMPT_NONE=y > # CONFIG_PREEMPT_VOLUNTARY is not set > # CONFIG_PREEMPT is not set > > Also the whole script is quite fast on latest kernels. I am guessing you > are chasing an already fixed problem. > > Hi Eric：
I had found out that the patch aaf92f(netfilter: conntrack: resched in nf_ct_iterate_cleanup) solve the problem, this patch add cond_sched() in the nf_ct_iterate_cleanup() which will be called in the net notifier chain every time, and I revert this patch at kernel 4.7-rc4 , it will panic for soft lockup, so I am not sure whether our patch is need, it looks like if I disable the CONFIG for netfilter that would register the nf_ct_iterate_cleanup as notifier, the problem still be exist. Thanks. Ding > > > . >
