Hi Ben, This patch is from Linhai, but I have the same concern about this. I will read ovs-rcu comments and feedback. Thanks for your time.
Best Regards, Wei Yanqin > -----Original Message----- > From: Ben Pfaff <b...@ovn.org> > Sent: Wednesday, June 3, 2020 8:35 AM > To: Yanqin Wei <yanqin....@arm.com> > Cc: Linhaifeng <haifeng....@huawei.com>; d...@openvswitch.org; nd > <n...@arm.com>; Lilijun (Jerry) <jerry.lili...@huawei.com>; chenchanghu > <chenchan...@huawei.com>; Lichunhe <lichu...@huawei.com> > Subject: Re: [ovs-dev] [PATCH v2] ovs rcu: update rcu pointer first > > This is not how RCU works in OVS. Every thread is by default considered > active. > They rarely quiesce except implicitly inside poll_block(). > Please read the large comment at the top of ovs-rcu.h. > > Is your patch based on actual bugs that you have found, or is it just some > kind > of precaution? If it is the latter, then it is not needed. > > On Tue, Jun 02, 2020 at 11:22:57PM +0000, Yanqin Wei wrote: > > Hi Ben, > > > > If my understanding is correct, the writer could not be a rcu thread > > because it > does not need report holding or not holding pointers. > > So old memory will be freed after all rcu thread report quiesce. > > > > Best Regards, > > Wei Yanqin > > > > > -----Original Message----- > > > From: Ben Pfaff <b...@ovn.org> > > > Sent: Wednesday, June 3, 2020 1:28 AM > > > To: Linhaifeng <haifeng....@huawei.com> > > > Cc: Yanqin Wei <yanqin....@arm.com>; d...@openvswitch.org; nd > > > <n...@arm.com>; Lilijun (Jerry) <jerry.lili...@huawei.com>; > > > chenchanghu <chenchan...@huawei.com>; Lichunhe > <lichu...@huawei.com> > > > Subject: Re: [ovs-dev] [PATCH v2] ovs rcu: update rcu pointer first > > > > > > On Tue, Jun 02, 2020 at 07:27:59AM +0000, Linhaifeng wrote: > > > > We should update rcu pointer first then use ovsrcu_postpone to > > > > free otherwise maybe cause use-after-free. > > > > e.g.,reader indicates momentary quiescent and access old pointer > > > > after writer postpone free old pointer and before setting new pointer. > > > > > > > > Signed-off-by: Linhaifeng <haifeng....@huawei.com> > > > > > > I don't see how that's possible, since the writer hasn't quiesced. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
