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Wed, 10 Dec 2025 17:38:19 GMT Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BC6A58043; Wed, 10 Dec 2025 17:38:19 +0000 (GMT) Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ADE8858059; Wed, 10 Dec 2025 17:38:13 +0000 (GMT) Received: from [9.43.108.138] (unknown [9.43.108.138]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 10 Dec 2025 17:38:13 +0000 (GMT) Message-ID: <7455ea1d-24a0-4f36-a744-3cd42b81c13a@linux.ibm.com> Date: Wed, 10 Dec 2025 23:08:11 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] sched/fair: Remove redundant error handling path in alloc_fair_sched_group To: Wanwu Li Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, Wanwu Li , Madadi Vineeth Reddy References: <20251208024043.2887311-1-liwanwu9113@163.com> Content-Language: en-US From: Madadi Vineeth Reddy In-Reply-To: <20251208024043.2887311-1-liwanwu9113@163.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: asvp19bPE7MYerOTWNlAOP36PBARTUcT X-Proofpoint-ORIG-GUID: V5RrxUjxvwYdNePVuWla8Df8lI9U2lq3 X-Authority-Analysis: v=2.4 cv=AdS83nXG c=1 sm=1 tr=0 ts=6939b00d cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=gGi0NRlIb6sjlJswAToA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjA2MDAwMCBTYWx0ZWRfXxH4CIaeHA6UI M68MEAq4oZ2bgWJnVeOKLPLT6FAbGFSDBA1I/RedGWcUqNlqQqh4SHL8A73DAInM4YEExj4MRGQ lQH+9EEpqOyQ0lI6djqthVwbyoU9hz6cnjkpOwm+7CxcrifZuS+MqXOkSxQE/mZuRdkS366gtkg E8vivk4PZxQi9tjN+5Rtj5NH7F/A6RCnupaHPk6gKEFo+f3DkTTQLG1dixXOBB6xdIpJ++/bZFx Cyz18Jo1Pqr0OPX37NKsAzcfDwXNOpR778qlqR1ZHUOpmU2s65EX/iJfNbeBOBa3afNOonDLGij zzt+YxoTWZ5/Z3bQYGTBPNt7/SHRgMJnj5p4WRT4UudkS6G1cFr8+k5nqX9C2LeuaAN+kST7LVw A4pGsRqMODJWOmuD7ZeCiJA68Nyl9A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-10_02,2025-12-09_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 priorityscore=1501 spamscore=0 phishscore=0 lowpriorityscore=0 bulkscore=0 clxscore=1011 malwarescore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2512060000 Hi Wanwu, On 08/12/25 08:10, Wanwu Li wrote: > From: Wanwu Li > > On error, the sched_free_group function already centrally handles > resource cleanup, making the explicit kfree(cfs_rq) in > alloc_fair_sched_group redundant. > > Signed-off-by: Wanwu Li > --- > kernel/sched/fair.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index da46c3164537..b657d3281f44 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -13645,7 +13645,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) > se = kzalloc_node(sizeof(struct sched_entity_stats), > GFP_KERNEL, cpu_to_node(i)); > if (!se) > - goto err_free_rq; > + goto err; > > init_cfs_rq(cfs_rq); > init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); > @@ -13654,8 +13654,6 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) > > return 1; > > -err_free_rq: > - kfree(cfs_rq); > err: > return 0; > } I believe this change introduces a memory leak. The `err_free_rq` label serves a specific purpose - it frees the cfs_rq that was allocated in the current loop iteration but failed before being registered with the task_group structure. Here is the flow with your patch: for_each_possible_cpu(i) { cfs_rq = kzalloc_node(sizeof(struct cfs_rq), GFP_KERNEL, cpu_to_node(i)); // Memory allocated, stored in local variable if (!cfs_rq) goto err; se = kzalloc_node(sizeof(struct sched_entity_stats), GFP_KERNEL, cpu_to_node(i)); // Say allocation fails here if (!se) goto err; // Jump directly to err (with your change) // Below is NEVER REACHED - cfs_rq not registered to tg->cfs_rq[i] init_cfs_rq(cfs_rq); init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); init_entity_runnable_average(se); The locally allocated cfs_rq pointer is lost because in `sched_free_group` that calls `free_fair_sched_group` is as below if (tg->cfs_rq) kfree(tg->cfs_rq[i]); // This is kfree(NULL) - the actual cfs_rq is leaked Thanks, Vineeth