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selftests: net: dsa: add a stress test for unlocked FDB operations

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This test is a bit strange in that it is perhaps more manual than
others: it does not transmit a clear OK/FAIL verdict, because user space
does not have synchronous feedback from the kernel. If a hardware access
fails, it is in deferred context.

Nonetheless, on sja1105 I have used it successfully to find and solve a
concurrency issue, so it can be used as a starting point for other
driver maintainers too.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean 2021-10-24 20:17:57 +03:00 committed by David S. Miller
parent d70b51f284
commit eccd0a80dc
2 changed files with 48 additions and 0 deletions
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@ -13056,6 +13056,7 @@ F: include/linux/dsa/
F: include/linux/platform_data/dsa.h
F: include/net/dsa.h
F: net/dsa/
F: tools/testing/selftests/drivers/net/dsa/
NETWORKING [GENERAL]
M: "David S. Miller" <davem@davemloft.net>

47
tools/testing/selftests/drivers/net/dsa/test_bridge_fdb_stress.sh Executable file
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@ -0,0 +1,47 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
# Bridge FDB entries can be offloaded to DSA switches without holding the
# rtnl_mutex. Traditionally this mutex has conferred drivers implicit
# serialization, which means their code paths are not well tested in the
# presence of concurrency.
# This test creates a background task that stresses the FDB by adding and
# deleting an entry many times in a row without the rtnl_mutex held.
# It then tests the driver resistance to concurrency by calling .ndo_fdb_dump
# (with rtnl_mutex held) from a foreground task.
# Since either the FDB dump or the additions/removals can fail, but the
# additions and removals are performed in deferred as opposed to process
# context, we cannot simply check for user space error codes.
WAIT_TIME=1
NUM_NETIFS=1
REQUIRE_JQ="no"
REQUIRE_MZ="no"
NETIF_CREATE="no"
lib_dir=$(dirname $0)/../../../net/forwarding
source $lib_dir/lib.sh
cleanup() {
echo "Cleaning up"
kill $pid && wait $pid &> /dev/null
ip link del br0
echo "Please check kernel log for errors"
}
trap 'cleanup' EXIT
eth=${NETIFS[p1]}
ip link del br0 2&>1 >/dev/null || :
ip link add br0 type bridge && ip link set $eth master br0
(while :; do
bridge fdb add 00:01:02:03:04:05 dev $eth master static
bridge fdb del 00:01:02:03:04:05 dev $eth master static
done) &
pid=$!
for i in $(seq 1 50); do
bridge fdb show > /dev/null
sleep 3
echo "$((${i} * 2))% complete..."
done