Re: [PATCH v3] net/sched: Set the flushing flags to false to prevent an infinite loop and add one test to tdc

[Simon Horman]

On Fri, Jun 09, 2023 at 11:31:15AM +0800, renmingshuai wrote:
> >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"
> >+        ]
> >+    }
> >+]
> 
> Ok. The new test is passed.
> [root@localhost tc-testing]# ./tdc.py -f tc-tests/infra/filter.json
> Test c2b4: Adding a new filter after flushing empty chain doesn't cause an infinite loop
> All test results:
> 1..1
> ok 1 c2b4 - Adding a new filter after flushing empty chain doesn't cause an infinite loop
> 
> Fixes: 726d061286ce ("net: sched: prevent insertion of new classifiers during chain flush")
> Signed-off-by: renmingshuai <renmingshuai@xxxxxxxxxx>

Hi renmingshuai,

the above text, in it's entirety, does not meet the needs
of a patch submission for the Linux kernel. In particular:

* All the context from previous discussion (the bits prefixed by '>')
  should be removed.
* The patch description should consist of just that, a description of
  the patch. Any relevant test results are also welcome here.
* Information about changes from previous versions should be provided
  in the form of a changelog, typically below the scissors (---).

A recent example is here:
- https://lore.kernel.org/all/20230607162353.3631199-1-mtottenh@xxxxxxxxxx/
  [PATCH v3] net/sched: act_pedit: Parse L3 Header for L4 offset

Also, please consider using spaces and capital letters
in your name in the from and signed-off parts of your submission.

e.g.: Mingshuai Ren <...> or Ren Mingshuai <...>

...

-- 
pw-bot: cr