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Date: Tue, 24 May 2022 13:51:24 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
linux-kernel@...r.kernel.org,
Daniel Borkmann <daniel@...earbox.net>
Subject: Re: kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes
address space '__rcu' of expression
On Mon, May 23, 2022 at 12:30:14PM +0200, Toke Høiland-Jørgensen wrote:
> kernel test robot <lkp@...el.com> writes:
>
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head: eaea45fc0e7b6ae439526b4a41d91230c8517336
> > commit: 782347b6bcad07ddb574422e01e22c92e05928c8 xdp: Add proper __rcu annotations to redirect map entries
> > date: 11 months ago
> > config: ia64-randconfig-s031-20220522 (https://download.01.org/0day-ci/archive/20220522/202205222029.xpW3PM1y-lkp@intel.com/config)
> > compiler: ia64-linux-gcc (GCC) 11.3.0
>
> Hmm, so this is ia64-only? Some kind of macro breakage? Paul, any ideas?
Line 1030 looks to me like it is doing everything correctly. I am not
sure why sparse would care about the architecture, but perhaps it does.
The unrcu_pointer() macro has not changed since March of 2020.
All I can suggest is to break that line up to make it easier to figure
out exactly what sparse is upset about.
Thanx, Paul
> -Toke
>
> > reproduce:
> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # apt-get install sparse
> > # sparse version: v0.6.4-dirty
> > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=782347b6bcad07ddb574422e01e22c92e05928c8
> > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > git fetch --no-tags linus master
> > git checkout 782347b6bcad07ddb574422e01e22c92e05928c8
> > # save the config file
> > mkdir build_dir && cp config build_dir/.config
> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=ia64 SHELL=/bin/bash kernel/bpf/
> >
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@...el.com>
> >
> >
> > sparse warnings: (new ones prefixed by >>)
> > kernel/bpf/devmap.c:561:29: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct bpf_dtab_netdev *dst @@ got struct bpf_dtab_netdev [noderef] __rcu * @@
> > kernel/bpf/devmap.c:561:29: sparse: expected struct bpf_dtab_netdev *dst
> > kernel/bpf/devmap.c:561:29: sparse: got struct bpf_dtab_netdev [noderef] __rcu *
> > kernel/bpf/devmap.c:657:29: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct bpf_dtab_netdev *dst @@ got struct bpf_dtab_netdev [noderef] __rcu * @@
> > kernel/bpf/devmap.c:657:29: sparse: expected struct bpf_dtab_netdev *dst
> > kernel/bpf/devmap.c:657:29: sparse: got struct bpf_dtab_netdev [noderef] __rcu *
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
> >
> > vim +/__rcu +1030 kernel/bpf/devmap.c
> >
> > 990
> > 991 static int dev_map_notification(struct notifier_block *notifier,
> > 992 ulong event, void *ptr)
> > 993 {
> > 994 struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
> > 995 struct bpf_dtab *dtab;
> > 996 int i, cpu;
> > 997
> > 998 switch (event) {
> > 999 case NETDEV_REGISTER:
> > 1000 if (!netdev->netdev_ops->ndo_xdp_xmit || netdev->xdp_bulkq)
> > 1001 break;
> > 1002
> > 1003 /* will be freed in free_netdev() */
> > 1004 netdev->xdp_bulkq = alloc_percpu(struct xdp_dev_bulk_queue);
> > 1005 if (!netdev->xdp_bulkq)
> > 1006 return NOTIFY_BAD;
> > 1007
> > 1008 for_each_possible_cpu(cpu)
> > 1009 per_cpu_ptr(netdev->xdp_bulkq, cpu)->dev = netdev;
> > 1010 break;
> > 1011 case NETDEV_UNREGISTER:
> > 1012 /* This rcu_read_lock/unlock pair is needed because
> > 1013 * dev_map_list is an RCU list AND to ensure a delete
> > 1014 * operation does not free a netdev_map entry while we
> > 1015 * are comparing it against the netdev being unregistered.
> > 1016 */
> > 1017 rcu_read_lock();
> > 1018 list_for_each_entry_rcu(dtab, &dev_map_list, list) {
> > 1019 if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
> > 1020 dev_map_hash_remove_netdev(dtab, netdev);
> > 1021 continue;
> > 1022 }
> > 1023
> > 1024 for (i = 0; i < dtab->map.max_entries; i++) {
> > 1025 struct bpf_dtab_netdev *dev, *odev;
> > 1026
> > 1027 dev = rcu_dereference(dtab->netdev_map[i]);
> > 1028 if (!dev || netdev != dev->dev)
> > 1029 continue;
> >> 1030 odev = unrcu_pointer(cmpxchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev), NULL));
> > 1031 if (dev == odev)
> > 1032 call_rcu(&dev->rcu,
> > 1033 __dev_map_entry_free);
> > 1034 }
> > 1035 }
> > 1036 rcu_read_unlock();
> > 1037 break;
> > 1038 default:
> > 1039 break;
> > 1040 }
> > 1041 return NOTIFY_OK;
> > 1042 }
> > 1043
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://01.org/lkp
>
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