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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae5a5839besm3357980a91.11.2026.10.28.07.41.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Oct 2026 07:41:32 -0700 (PDT) Message-ID: Date: Wed, 28 Oct 2026 22:41:28 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] selftests: cpufreq: stop CPU hotplug loop after cpufreq update test To: xiong yining , "Rafael J . Wysocki" , Viresh Kumar , Shuah Khan Cc: linux-pm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, chenbaozi@phytium.com.cn, zhongqiu.han@oss.qualcomm.com References: <20261028100241.189085-1-xiongyining1480@phytium.com.cn> Content-Language: en-US From: Zhongqiu Han In-Reply-To: <20261028100241.189085-1-xiongyining1480@phytium.com.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDI4MDA1OCBTYWx0ZWRfX2tpAbcxCXUC1 w09T/M+4jgFjOXrQfXoMq/bu3xUpdnP6L3h7F/lc7VGm/L7/xnrdmyNpIMnkIyHoTyKPeIIXK7y r0rv4y2MEtaD87qAkzaeMMuf7xJkgahQwD0dwvQMcN2fOCw/oMEEpiC5IfsOAyKR+M5pTajupVH zX+O6IDKqR0sjOeu7oGamSN71G97+Rc/ArCKSu9ZrAXSe4sF0S0J/f/KzxBY6mxhdGn5s4jRVgK 95Xc/tKv8WKgcJnQoLanQWu7DtULtmjJ7bbul+4jlY64ToxPJ7vUey3KbwBB0owkrujYLQ+Sgot wn/+ZO5I9RHbh3jMUeITsx8V4vNuAPvGXpCS2xOZ06QBK/0lg1xiyfu7dOEeqEwuNIYgts5EAg5 ljfiw4+4VuH/vTLOJTPS9g/E0Hmx2hcEmVkt0L3KwbPCCd1C6ufZS34G9kMjCescWkoKzFneMfN Y3zIP7TCWn6KHDDHI8A== X-Proofpoint-GUID: yJ7Xr6E_Nw9oPKzWIC08Jrbez2I7HKTt X-Proofpoint-ORIG-GUID: yJ7Xr6E_Nw9oPKzWIC08Jrbez2I7HKTt X-Authority-Analysis: v=2.4 cv=LdipeTfi c=1 sm=1 tr=0 ts=6ae2099e cx=c_pps a=UNFcQwm+pnOIJct1K4W+Mw==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=Vt2AcnKqAAAA:8 a=VwQbUJbxAAAA:8 a=c92rfblmAAAA:8 a=fgrLqfBXAAAA:8 a=rLnwe5TcSjkNIz7vCUkA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=uKXjsCUrEbL0IQVhDsJ9:22 a=v10HlyRyNeVhbzM4Lqgd:22 a=GvGzcOZaWPEFPQC_NcjD:22 a=_Ge82aPy-h_wFa7gWU4u:22 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDI4MDA1OCBTYWx0ZWRfX8Il0KvTw0paC oR+35oqh5+rOOgL1JqJ9ypxLTeLgtTrmq8PmrLHoHIg19z5rAAn+KKQxKUFFdMAsaTT1kYR3WG8 gI7/EhDdBR2yRdrhtcZa2kGdHsFckCk= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-28_04,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 adultscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 impostorscore=0 suspectscore=0 lowpriorityscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610280058 Hi, On 10/28/2026 6:02 PM, xiong yining wrote: > Original test uses a fixed 5000 iteration loop to trigger CPU hotplug > for verifying cpufreq synchronization between CPU hotplug and sysfs > writes. > > Two issues exist: > 1. Background hotplug task keeps running after test completes, causing > redundant CPU on/offline operations. > 2. When cpufreq frequency setup is slow, the hotplug loop may exit > before frequency updates finish, which breaks test purpose. > > Introduce a file-based stop flag to control the infinite hotplug loop. > After all cpufreq updates complete, create the stop flag file and > wait for the hotplug task to exit. The changelog still describes the v1 stop-file approach; please update it. > > This makes hotplug run only during cpufreq sysfs write test, > align with test objective. > > Signed-off-by: xiong yining > --- > Changes in v2: > - Stop the hotplug child process by signal notification instead of > a stop file, avoiding the predictable temporary path. > - Add an exit trap so the hotplug child is also cleaned up when the > main shell terminates abnormally. > - Link to v1: > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2662696.html > > This addresses the security and robustness concerns raised by Sashiko. > --- > .../selftests/cpufreq/special-tests.sh | 30 +++++++++++++++---- > 1 file changed, 24 insertions(+), 6 deletions(-) > > diff --git a/tools/testing/selftests/cpufreq/special-tests.sh b/tools/testing/selftests/cpufreq/special-tests.sh > index e87ed7c8e5e5..b3ebead1c52a 100755 > --- a/tools/testing/selftests/cpufreq/special-tests.sh > +++ b/tools/testing/selftests/cpufreq/special-tests.sh > @@ -16,6 +16,8 @@ source cpu.sh > source cpufreq.sh > source governor.sh > > +HOTPLUG_PID="" > + > # Test 1 > # $1: policy > __simple_lockdep() > @@ -92,20 +94,34 @@ governor_race() > restore_all_governors > } > > +hotplug_cleanup() > +{ > + if [[ -n "$HOTPLUG_PID" ]]; then > + kill -s SIGTERM "$HOTPLUG_PID" > + wait "$HOTPLUG_PID" > + > + HOTPLUG_PID="" > + fi > +} > + > # Test 4 > # $1: cpu > hotplug_with_updates_cpu() > { > local filepath="$CPUROOT/$1/cpufreq" > > + ( > + local quit=0 > + trap 'quit=1' SIGTERM > + while [ "$quit" -eq 0 ]; do > + reboot_cpu "$1" > + done > + ) & > + HOTPLUG_PID=$! > + > # switch to ondemand > __switch_governor_for_cpu $1 "ondemand" > > - for i in `seq 1 5000` > - do > - reboot_cpu $1 > - done & > - > local freqs=$(cat $filepath/scaling_available_frequencies) > local oldfreq=$(cat $filepath/scaling_min_freq) The background hotplug loop is now started before switching to ondemand and before reading scaling_available_frequencies / scaling_min_freq. If the CPU happens to be offline at that point (such as single-CPU policy), those accesses return -EBUSY: the governor switch is lost, freqs is empty so the update loop does nothing while the test still passes, and oldfreq is empty so scaling_min_freq is not restored. Please start the hotplug subshell only after that setup is done. > > @@ -117,14 +133,16 @@ hotplug_with_updates_cpu() > done > done > > + hotplug_cleanup > + > # restore old freq > echo $oldfreq > $filepath/scaling_min_freq > } > > hotplug_with_updates() > { > + trap 'hotplug_cleanup' EXIT AFAIK, regarding the EXIT-trap-on-signal remark from Sashiko: https://sashiko.dev/#/patchset/20261028100241.189085-1-xiongyining1480%40phytium.com.cn Bash runs the EXIT trap on SIGINT, SIGTERM, and SIGHUP, so I don't think additional traps are necessary. This issue occurs with Dash, but not with Bash. One sample simulation script： #!/bin/bash for sh in bash dash; do command -v $sh >/dev/null || continue for s in INT TERM HUP; do out=$(env --default-signal=INT $sh -c \ 'echo "$(readlink /proc/$$/exe)" trap "echo EXIT-trap-ran" EXIT kill -'$s' $$ sleep 1 echo not-killed' 2>/dev/null) rc=$? self=$(echo "$out" | sed -n 1p) res=$(echo "$out" | sed -n 2p) printf "%-14s %-4s rc=%-3s %s\n" "$self" $s $rc "${res:-}" done done output: /usr/bin/bash INT rc=130 EXIT-trap-ran /usr/bin/bash TERM rc=143 EXIT-trap-ran /usr/bin/bash HUP rc=129 EXIT-trap-ran /usr/bin/dash INT rc=130 /usr/bin/dash TERM rc=143 /usr/bin/dash HUP rc=129 > save_all_governors > for_each_non_boot_cpu hotplug_with_updates_cpu > - wait > restore_all_governors > } -- Thx and BRs, Zhongqiu Han