Re: [PATCH v2] net/sched: Set the flushing flags to false to prevent an infinite loop and add one test to tdc

[Pedro Tammela]

On 08/06/2023 09:32, renmingshuai wrote:
> > On 07/06/2023 01:19, renmingshuai wrote:
> > > > On 06/06/2023 11:45, renmingshuai wrote:
> > > > > When a new chain is added by using tc, one soft lockup alarm will
> > > > > be
> > > > >     generated after delete the prio 0 filter of the chain. To
> > > > >     reproduce
> > > > >     the problem, perform the following steps:
> > > > > (1) tc qdisc add dev eth0 root handle 1: htb default 1
> > > > > (2) tc chain add dev eth0
> > > > > (3) tc filter del dev eth0 chain 0 parent 1: prio 0
> > > > > (4) tc filter add dev eth0 chain 0 parent 1:
> > > >
> > > > This seems like it could be added to tdc or 3 and 4 must be run in
> > > > parallel?
> > > 3 and 4 do not need to be run inparallel. When a new chain is added
> > > by the
> > >    way as step 1 and the step 3 is completed, this problem always
> > >    occurs
> > >    whenever step 4 is run.
> >
> > Got it,
> > The test still hangs with the provided patch.
> >
> > + tc qdisc add dev lo root handle 1: htb default 1
> > + tc chain add dev lo
> > + tc filter del dev lo chain 0 parent 1: prio 0
> > [   68.790030][ T6704] [+]
> > [   68.790060][ T6704] chain refcnt 2
> > [   68.790951][ T6704] [-]
> > + tc filter add dev lo chain 0 parent 1:
> > <hangs>
> >
> > Also please add this test to tdc, it should be straightforward.
> Sorry for not testing before. I forgot that the chain->refcnt was
> increased by 1 when tcf_chain_get() is called in tc_del_tfilter().
>   The value of chain->refcnt is 2 after chain flush. The test
>   result is as follows:
> [root@localhost ~]# tc qdisc add dev eth2 root handle 1: htb default 1
> [root@localhost ~]# tc chain add dev eth2
> [root@localhost ~]# tc filter del dev eth2 chain 0 parent 1: prio 0
> [root@localhost ~]# tc filter add dev eth2 chain 0 parent 1:
> Error: Filter kind and protocol must be specified.
> We have an error talking to the kernel
>
> And I have add this test to tdc:
> [root@localhost tc-testing]# ./tdc.py -f tc-tests/filters/tests.json
> ok 7 c2b4 - Adding a new fiter after deleting a filter in a chain does
> not cause  an infinite loop
>
> Fixes: 726d061286ce ("net: sched: prevent insertion of new classifiers during chain flush")
> Signed-off-by: renmingshuai <renmingshuai@xxxxxxxxxx>

Please respin with the following applied:

diff --git 
a/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json 
b/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
index c759c3db9a37..361235ad574b 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
@@ -125,25 +125,5 @@
         "teardown": [
             "$TC qdisc del dev $DEV2 ingress"
         ]
-    },
-    {
-        "id": "c2b4",
-        "name": "Adding a new fiter after deleting a filter in a chain 
does not cause an infinite loop",
-        "category": [
-            "filter",
-            "prio"
-        ],
-        "setup": [
-            "$TC qdisc add dev $DEV1 root handle 1: htb default 1",
-            "$TC chain add dev $DEV1"
-        ],
-        "cmdUnderTest": "$TC filter del dev $DEV1 chain 0 parent 1: 
prio 0",
-        "expExitCode": "0",
-        "verifyCmd": "$TC filter add dev $DEV1 chain 0 parent 1:",
-        "matchPattern": "Error: Filter kind and protocol must be 
specified.",
-        "matchCount": "1",
-        "teardown": [
-            "$TC qdisc del dev $DEV1 root handle 1: htb default 1"
-        ]
     }
 ]
diff --git 
a/tools/testing/selftests/tc-testing/tc-tests/infra/filters.json 
b/tools/testing/selftests/tc-testing/tc-tests/infra/filters.
json
new file mode 100644
index 000000000000..55d6f209c388
--- /dev/null
+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/filters.json
@@ -0,0 +1,24 @@
+[
+    {
+        "id": "c2b4",
+        "name": "Adding a new filter after flushing empty chain doesnt 
cause an infinite loop",
+        "category": [
+            "filter",
+            "chain"
+        ],
+        "setup": [
+            "$IP link add dev $DUMMY type dummy || /bin/true",
+            "$TC qdisc add dev $DUMMY root handle 1: htb default 1",
+            "$TC chain add dev $DUMMY",
+            "$TC filter del dev $DUMMY chain 0 parent 1: prio 0"
+        ],
+        "cmdUnderTest": "$TC filter add dev $DUMMY chain 0 parent 1:",
+        "expExitCode": "2",
+        "verifyCmd": "$TC chain ls dev $DUMMY",
+        "matchPattern": "chain parent 1: chain 0",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY root handle 1: htb default 1"
+        ]
+    }
+]