From: Ding Tianhong Subject: Re: [PATCH] ipv6: Fix soft lockup for ipv6 network notifier. Date: Fri, 1 Jul 2016 16:10:55 +0800 Message-ID: <5776258F.6080008@huawei.com> References: <57761E04.8030202@huawei.com> <1467359847.11238.34.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: , , , Eric Dumazet , "David S. Miller" , Netdev , Cong Wang To: Eric Dumazet Return-path: In-Reply-To: <1467359847.11238.34.camel@edumazet-glaptop3.roam.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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. Thanks Ding > Thanks. > > > > > . >