On Wed 07 Aug 2019 at 04:13, wenxu@xxxxxxxxx wrote:
> From: wenxu <wenxu@xxxxxxxxx>
>
> It provide a callback list to find the blocks of tc
> and nft subsystems
>
> Signed-off-by: wenxu <wenxu@xxxxxxxxx>
> Acked-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
> ---
> v7: add a mutex lock for add/del flow_indr_block_ing_cb
>
> include/net/flow_offload.h | 10 ++++++++-
> net/core/flow_offload.c | 51 ++++++++++++++++++++++++++++++++++------------
> net/sched/cls_api.c | 9 +++++++-
> 3 files changed, 55 insertions(+), 15 deletions(-)
>
> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
> index 46b8777..e8069b6 100644
> --- a/include/net/flow_offload.h
> +++ b/include/net/flow_offload.h
> @@ -379,6 +379,15 @@ typedef void flow_indr_block_ing_cmd_t(struct net_device *dev,
> void *cb_priv,
> enum flow_block_command command);
>
> +struct flow_indr_block_ing_entry {
> + flow_indr_block_ing_cmd_t *cb;
> + struct list_head list;
> +};
> +
> +void flow_indr_add_block_ing_cb(struct flow_indr_block_ing_entry *entry);
> +
> +void flow_indr_del_block_ing_cb(struct flow_indr_block_ing_entry *entry);
> +
> int __flow_indr_block_cb_register(struct net_device *dev, void *cb_priv,
> flow_indr_block_bind_cb_t *cb,
> void *cb_ident);
> @@ -395,7 +404,6 @@ void flow_indr_block_cb_unregister(struct net_device *dev,
> void *cb_ident);
>
> void flow_indr_block_call(struct net_device *dev,
> - flow_indr_block_ing_cmd_t *cb,
> struct flow_block_offload *bo,
> enum flow_block_command command);
>
> diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
> index 4cc18e4..64c3d4d 100644
> --- a/net/core/flow_offload.c
> +++ b/net/core/flow_offload.c
> @@ -3,6 +3,7 @@
> #include <linux/slab.h>
> #include <net/flow_offload.h>
> #include <linux/rtnetlink.h>
> +#include <linux/mutex.h>
>
> struct flow_rule *flow_rule_alloc(unsigned int num_actions)
> {
> @@ -282,6 +283,8 @@ int flow_block_cb_setup_simple(struct flow_block_offload *f,
> }
> EXPORT_SYMBOL(flow_block_cb_setup_simple);
>
> +static LIST_HEAD(block_ing_cb_list);
> +
> static struct rhashtable indr_setup_block_ht;
>
> struct flow_indr_block_cb {
> @@ -295,7 +298,6 @@ struct flow_indr_block_dev {
> struct rhash_head ht_node;
> struct net_device *dev;
> unsigned int refcnt;
> - flow_indr_block_ing_cmd_t *block_ing_cmd_cb;
> struct list_head cb_list;
> };
>
> @@ -389,6 +391,20 @@ static void flow_indr_block_cb_del(struct flow_indr_block_cb *indr_block_cb)
> kfree(indr_block_cb);
> }
>
> +static void flow_block_ing_cmd(struct net_device *dev,
> + flow_indr_block_bind_cb_t *cb,
> + void *cb_priv,
> + enum flow_block_command command)
> +{
> + struct flow_indr_block_ing_entry *entry;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(entry, &block_ing_cb_list, list) {
> + entry->cb(dev, cb, cb_priv, command);
> + }
> + rcu_read_unlock();
> +}
Hi,
I'm getting following incorrect rcu usage warnings with this patch
caused by rcu_read_lock in flow_block_ing_cmd:
[ 401.510948] =============================
[ 401.510952] WARNING: suspicious RCU usage
[ 401.510993] 5.3.0-rc3+ #589 Not tainted
[ 401.510996] -----------------------------
[ 401.511001] include/linux/rcupdate.h:265 Illegal context switch in RCU read-side critical section!
[ 401.511004]
other info that might help us debug this:
[ 401.511008]
rcu_scheduler_active = 2, debug_locks = 1
[ 401.511012] 7 locks held by test-ecmp-add-v/7576:
[ 401.511015] #0: 00000000081d71a5 (sb_writers#4){.+.+}, at: vfs_write+0x166/0x1d0
[ 401.511037] #1: 000000002bd338c3 (&of->mutex){+.+.}, at: kernfs_fop_write+0xef/0x1b0
[ 401.511051] #2: 00000000c921c634 (kn->count#317){.+.+}, at: kernfs_fop_write+0xf7/0x1b0
[ 401.511062] #3: 00000000a19cdd56 (&dev->mutex){....}, at: sriov_numvfs_store+0x6b/0x130
[ 401.511079] #4: 000000005425fa52 (pernet_ops_rwsem){++++}, at: unregister_netdevice_notifier+0x30/0x140
[ 401.511092] #5: 00000000c5822793 (rtnl_mutex){+.+.}, at: unregister_netdevice_notifier+0x35/0x140
[ 401.511101] #6: 00000000c2f3507e (rcu_read_lock){....}, at: flow_block_ing_cmd+0x5/0x130
[ 401.511115]
stack backtrace:
[ 401.511121] CPU: 21 PID: 7576 Comm: test-ecmp-add-v Not tainted 5.3.0-rc3+ #589
[ 401.511124] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
[ 401.511127] Call Trace:
[ 401.511138] dump_stack+0x85/0xc0
[ 401.511146] ___might_sleep+0x100/0x180
[ 401.511154] __mutex_lock+0x5b/0x960
[ 401.511162] ? find_held_lock+0x2b/0x80
[ 401.511173] ? __tcf_get_next_chain+0x1d/0xb0
[ 401.511179] ? mark_held_locks+0x49/0x70
[ 401.511194] ? __tcf_get_next_chain+0x1d/0xb0
[ 401.511198] __tcf_get_next_chain+0x1d/0xb0
[ 401.511251] ? uplink_rep_async_event+0x70/0x70 [mlx5_core]
[ 401.511261] tcf_block_playback_offloads+0x39/0x160
[ 401.511276] tcf_block_setup+0x1b0/0x240
[ 401.511312] ? mlx5e_rep_indr_setup_tc_cb+0xca/0x290 [mlx5_core]
[ 401.511347] ? mlx5e_rep_indr_tc_block_unbind+0x50/0x50 [mlx5_core]
[ 401.511359] tc_indr_block_get_and_ing_cmd+0x11b/0x1e0
[ 401.511404] ? mlx5e_rep_indr_tc_block_unbind+0x50/0x50 [mlx5_core]
[ 401.511414] flow_block_ing_cmd+0x7e/0x130
[ 401.511453] ? mlx5e_rep_indr_tc_block_unbind+0x50/0x50 [mlx5_core]
[ 401.511462] __flow_indr_block_cb_unregister+0x7f/0xf0
[ 401.511502] mlx5e_nic_rep_netdevice_event+0x75/0xb0 [mlx5_core]
[ 401.511513] unregister_netdevice_notifier+0xe9/0x140
[ 401.511554] mlx5e_cleanup_rep_tx+0x6f/0xe0 [mlx5_core]
[ 401.511597] mlx5e_detach_netdev+0x4b/0x60 [mlx5_core]
[ 401.511637] mlx5e_vport_rep_unload+0x71/0xc0 [mlx5_core]
[ 401.511679] esw_offloads_disable+0x5b/0x90 [mlx5_core]
[ 401.511724] mlx5_eswitch_disable.cold+0xdf/0x176 [mlx5_core]
[ 401.511759] mlx5_device_disable_sriov+0xab/0xb0 [mlx5_core]
[ 401.511794] mlx5_core_sriov_configure+0xaf/0xd0 [mlx5_core]
[ 401.511805] sriov_numvfs_store+0xf8/0x130
[ 401.511817] kernfs_fop_write+0x122/0x1b0
[ 401.511826] vfs_write+0xdb/0x1d0
[ 401.511835] ksys_write+0x65/0xe0
[ 401.511847] do_syscall_64+0x5c/0xb0
[ 401.511857] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 401.511862] RIP: 0033:0x7fad892d30f8
[ 401.511868] Code: 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 25 96 0d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 60 c3 0f 1f 80 00 00 00 00 48 83
ec 28 48 89
[ 401.511871] RSP: 002b:00007ffca2a9fad8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 401.511875] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fad892d30f8
[ 401.511878] RDX: 0000000000000002 RSI: 000055afeb072a90 RDI: 0000000000000001
[ 401.511881] RBP: 000055afeb072a90 R08: 00000000ffffffff R09: 000000000000000a
[ 401.511884] R10: 000055afeb058710 R11: 0000000000000246 R12: 0000000000000002
[ 401.511887] R13: 00007fad893a8780 R14: 0000000000000002 R15: 00007fad893a3740
I don't think it is correct approach to try to call these callbacks with
rcu protection because:
- Cls API uses sleeping locks that cannot be used in rcu read section
(hence the included trace).
- It assumes that all implementation of classifier ops reoffload() don't
sleep.
- And that all driver offload callbacks (both block and classifier
setup) don't sleep, which is not the case.
I don't see any straightforward way to fix this, besides using some
other locking mechanism to protect block_ing_cb_list.
Regards,
Vlad
