On Sat, Mar 18, 2017 at 9:03 PM, Kaiwen Xu <kaiwen...@hulu.com> wrote: > On Sat, Mar 18, 2017 at 08:49:43PM -0700, Cong Wang wrote: >> On Sat, Mar 18, 2017 at 6:48 PM, Kevin Xu <kaiwen...@hulu.com> wrote: >> > In some rare cases, inet_sk_rx_dst_set() may be called multiple times >> > on the same dst, causing double refcounting. Eventually, it >> > prevents net_device to be destroyed. The bug manifested as >> > >> > unregister_netdevice: waiting for lo to become free. Usage count = 1 >> > >> > in the kernel log, preventing new network namespace creation. >> > >> > Signed-off-by: Kevin Xu <kaiwen...@hulu.com> >> >> Don't know why you don't follow the discussion on your v1... >> >> It is protected by bh_lock_sock(), so your patch is not needed >> at all. >> >> Read net/ipv4/udp.c: >> >> 1762 /* For TCP sockets, sk_rx_dst is protected by socket lock >> 1763 * For UDP, we use xchg() to guard against concurrent changes. >> 1764 */ > > I probably misunderstood. Do you mean v2 patch is actually not needed or > the whole workaround is not necessary?
Your patch, no matter v1 or v2, is not needed because we use bh_lock_sock() to serialize inet_sk_rx_dst_set(), unless you find a case where we miss the bh_lock_sock(), but you don't say it in your changelog. "some rare cases" is not enough to justify this bug.
