On Wed, 2017-02-08 at 12:27 +0200, Kalle Valo wrote: > Paolo Abeni <pabeni@xxxxxxxxxx> writes: > > > On Tue, 2017-02-07 at 20:23 +0100, Arend Van Spriel wrote: > > > On 7-2-2017 17:50, Paolo Abeni wrote: > > > > the skbs can be held by the driver for a long time, so we need > > > > to clear any state on xmit to avoid hanging other subsystems. > > > > The skbs are already orphaned later in cmsg code, so we just > > > > need to clear the nf/dst/secpath. > > > > Do it early, while the relevant entries are hopefully still > > > > hot in the cache. > > > > > > What is this about really? A bit more background about the issue > > > might > > > help understanding the need for this patch. Is this really specific > > > to > > > brcmfmac. For instance is something similar already done in mac80211? > > > > The issue is apparently driver specific, as reported in: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1294415 > > > > This is caused by xmit skbs carrying a notrack ct entry not being freed > > by the device driver in a timely manner. Removing the ct module waits > > for such entries refcount going to zero and hangs the kernel in busy > > loop (for several minutes). > > > > The relevant skbs are icmp6 packets (ND if I recall correctly, they > > bcast packets at the mac level). > > > > The only other known device driver suffering for the issue is the > > infiniband ipoib driver, I send a separate patch for it. > > > > I lack the broadcom h/w, but with infiniband the bug can be reproduced > > with the following steps: > > > > - ensure ipv6 is enabled on the target device, and firewalld is running > > (e.g. the module nf_conntrack_ipv6 is loaded) > > - assign a static ip to the device > > - shut down the firewall (e.g. try to remove the module nf_conntrack) > > > > For the brcmfmac driver most probably it is necessary being > > disassociated from the AP before shutting down the firewall (but I > > can't double check). This is probably why mac80211 does not suffer this > > issue. > > > > The root cause for the issue could be actually a firmware issue, any > > better clues are more than welcome! > > BTW, you should have added all this to the commit log. After reading the > original description it left more questions open than answered them. I'm sorry for the lack of clarity, thank you for the advice, will do next time. I tried to keep the commit message short since others reviewer in other area of the kernel really prefer shorter ones. Cheers, Paolo
