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Mon, 6 Oct 2025 15:21:33 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8776720043; Mon, 6 Oct 2025 15:21:33 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CBA7720040; Mon, 6 Oct 2025 15:21:28 +0000 (GMT) Received: from [9.124.214.120] (unknown [9.124.214.120]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 6 Oct 2025 15:21:28 +0000 (GMT) Message-ID: Date: Mon, 6 Oct 2025 20:51:27 +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 01/14] sched: Employ sched_change guards To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, longman@redhat.com, hannes@cmpxchg.org, mkoutny@suse.com, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, cgroups@vger.kernel.org, sched-ext@lists.linux.dev, liuwenfang@honor.com, tglx@linutronix.de, tj@kernel.org References: <20250910154409.446470175@infradead.org> <20250910155808.415580225@infradead.org> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20250910155808.415580225@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDA0MDAxOCBTYWx0ZWRfX19dQ+iwBtKSY RZYC63N/LKEDG4lvHmvFk4kqeUdiKTUkoeEydIQj0gERIPYb7wzu/dT3ruYfzf0tqk6hSEPnSJj vAceTL/D9jZp5YcHo5/G2yjcE/7XmF1v6nE6NAkYgZ6tDoR0jpPyotWtdVuKa2+VLswggC2e5aM wkOBU6yYwsfngbRIOOikjDuah2PY3FhN0G/RycWSMvphVFMQ2ydddJ0JrfDYoMfkl8NBoVhmP5a B4bxump1C9JbRjLmdH28j2Hm+k8erlXktgMgwIhqZFW+ew57epmRULGEpyL0Q+vqyhgabfuvw/Y 3OP2j05K18HHNX1Y69N+8Bmb7l9iAq77MpkwPey4rD80S0Wa5dDtdYAj/RkTbi8eGzwwD4M16TX kCpJp80qt5/9NnlUxs1edOuughRksg== X-Authority-Analysis: v=2.4 cv=I4dohdgg c=1 sm=1 tr=0 ts=68e3de81 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=hKsuor804cSa_We8IwkA:9 a=QEXdDO2ut3YA:10 a=nl4s5V0KI7Kw-pW0DWrs:22 a=pHzHmUro8NiASowvMSCR:22 a=xoEH_sTeL_Rfw54TyV31:22 X-Proofpoint-GUID: 05FclDpPzSC4xn8YbrD0TJ5uabLK3hwr X-Proofpoint-ORIG-GUID: eWovQ_0FPZV6sBTIKMBJldvpkfSp2N_a X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-06_05,2025-10-02_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 spamscore=0 bulkscore=0 suspectscore=0 clxscore=1011 priorityscore=1501 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2509150000 definitions=main-2510040018 On 9/10/25 9:14 PM, Peter Zijlstra wrote: > As proposed a long while ago -- and half done by scx -- wrap the > scheduler's 'change' pattern in a guard helper. > [...]> put_task_struct(p); > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -3860,23 +3860,22 @@ extern void check_class_changed(struct r > extern struct balance_callback *splice_balance_callbacks(struct rq *rq); > extern void balance_callbacks(struct rq *rq, struct balance_callback *head); > > -#ifdef CONFIG_SCHED_CLASS_EXT > -/* > - * Used by SCX in the enable/disable paths to move tasks between sched_classes > - * and establish invariants. > - */ > -struct sched_enq_and_set_ctx { > +struct sched_change_ctx { > struct task_struct *p; > - int queue_flags; > + int flags; > bool queued; > bool running; > }; > > -void sched_deq_and_put_task(struct task_struct *p, int queue_flags, > - struct sched_enq_and_set_ctx *ctx); > -void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx); > +struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigned int flags); > +void sched_change_end(struct sched_change_ctx *ctx); > > -#endif /* CONFIG_SCHED_CLASS_EXT */ > +DEFINE_CLASS(sched_change, struct sched_change_ctx *, > + sched_change_end(_T), > + sched_change_begin(p, flags), > + struct task_struct *p, unsigned int flags) > + > +DEFINE_CLASS_IS_UNCONDITIONAL(sched_change) > > #include "ext.h" > could you please add a comment on matching flags on dequeue/enqueue here? Since the ctx->flags don't get cleared, one could be left wondering how does the enqueue happens(exp: ENQUEUE_RESTORE) until they see it works since flags match.