From nobody Wed Oct 8 09:09:14 2025 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 05F3186328 for ; Tue, 1 Jul 2025 00:38:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.177.32 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751330320; cv=none; b=F0IXHDd1AIcoO4D5IpIoXK4pfk4QzUulc4/IMEI2d4T3qF98ENf01cB8Q7ydYZjz+mcGpY4SjEvqkI0j1qacRpsjoy7A8vF63f4cIjJDG3vpOo/k7/+3cbDlCjz/+i/TwqOWT4G6SQttWNaWCW/iyZC/JRt7oOyzr4PHQIG9eTo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751330320; c=relaxed/simple; bh=cB+AyQBm3Vfw1IrDC1azeCRsmvjxinflrt0ymlU5Yrk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IyhJP7zSwTmZOjrsOgXDde/bzuSQorFjjfjF+l5BbY+bS/vAursJzumB7mFdayvMly/cYIZxQ4qH8c+kHCdEGeNTgOYRLk4x1/JnQJWCOo8cO2Z7R2gLTt65l1Bw9ot1KWoRAHQKjjVR0ld5o9CaG23MxDaIO+7eDQFONW9Sox8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oracle.com; spf=pass smtp.mailfrom=oracle.com; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b=gMPBJMUU; arc=none smtp.client-ip=205.220.177.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oracle.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oracle.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="gMPBJMUU" Received: from pps.filterd (m0246632.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 55UIBxpL003650; Tue, 1 Jul 2025 00:38:08 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-transfer-encoding:date:from:in-reply-to:message-id :mime-version:references:subject:to; s=corp-2025-04-25; bh=FsY2D KKLC/0tkiNL1jCbJcYDiNBCsD6bXamS8zhaBV0=; b=gMPBJMUUb8jcKH8qPTgiK TX4IzAWpNYjcCDFJm7aXBAntmr9pLpi/lW8YkigvPREmuDjb9MJbil9lS7ZKuzjk ExMITAgLT9Rzyah/hsPGJsL76v6ha2IgVEJLXSaJOg4VswY2GRFqT0j1gkM/UywO h6rwaW3jEWCDJUUi5bmmfexRmyfT85UHZHcB4wVT6QpDBu1XmmxUsE43fvkFpuz6 yVOhivleryLwCsMRHAOA4NDtEldyszLGOpSHMSp48NIKWcLR15PPG3sD2GcKecjf D652uvbGwyIRA7JP/vqWsoEqorNdlqr2jRxZZiGuAX6yH6DHZ2BG52fCGhTgAqrH Q== Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.appoci.oracle.com [147.154.18.20]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 47j80w3k31-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 01 Jul 2025 00:38:08 +0000 (GMT) Received: from pps.filterd (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 55UNDxNY009139; Tue, 1 Jul 2025 00:38:07 GMT Received: from psang-work.osdevelopmeniad.oraclevcn.com (psang-work.allregionaliads.osdevelopmeniad.oraclevcn.com [100.100.253.35]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 47j6u92pxj-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 01 Jul 2025 00:38:07 +0000 From: Prakash Sangappa To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, bigeasy@linutronix.de, kprateek.nayak@amd.com, vineethr@linux.ibm.com Subject: [PATCH V6 2/7] Sched: Indicate if thread got rescheduled Date: Tue, 1 Jul 2025 00:37:44 +0000 Message-ID: <20250701003749.50525-3-prakash.sangappa@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250701003749.50525-1-prakash.sangappa@oracle.com> References: <20250701003749.50525-1-prakash.sangappa@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-06-30_06,2025-06-27_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 spamscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2507010002 X-Proofpoint-GUID: rlaOoYskALshdZfrp_gZQ07_gQ9Fv-4a X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzAxMDAwMiBTYWx0ZWRfXy9e0Tb92UX8i QAsGFTYCOMiCo9tZJYdOJDOf+2SnIXSlhPVQB+/P9+jkP4bdNWC3Gai3Wfs5+ca6jW3edKGZZKB F4lUz/zTqm797RvKW9KSNCFKrNRYG5tiJcsgG+AiFlK3/je3c+mmAEG1kjhP8vFoluV1tEVIT8V TU29wBCvIuB/8REO8UvRRk5EsjxRbP3O5tEYJTXvXo5XB6SpkLkeJHqdAFnbkxd1QOl5iL8ksjd 7b0eV6NfAR5ZZ6sYC9E139g1+oGaJFl2Ylw8wEau4yXAKSomIFEuCGtai2QnhQIOgjSu7XZZied emiZUfYTqi8Kbby88lMI5NtEOc78YxgKBaPnoxh+CUo6MXGkTnv8uU+xb7kErl/cj/cRNTeaZ5L ch5IplX0tLADdFDvyTWUCyrFajrr0co0REaQZCm+7cFfR6heduaUTbOLI6sjRbzoT8kz4A/l X-Authority-Analysis: v=2.4 cv=D6hHKuRj c=1 sm=1 tr=0 ts=68632df0 b=1 cx=c_pps a=e1sVV491RgrpLwSTMOnk8w==:117 a=e1sVV491RgrpLwSTMOnk8w==:17 a=Wb1JkmetP80A:10 a=yPCof4ZbAAAA:8 a=qx7APbdOUbj-W9D39agA:9 cc=ntf awl=host:14723 X-Proofpoint-ORIG-GUID: rlaOoYskALshdZfrp_gZQ07_gQ9Fv-4a Content-Type: text/plain; charset="utf-8" Use a bit in rseq flags to indicate if the thread got rescheduled after the cpu time extension was graned. The user thread can check this flag before calling sched_yield() to yield the cpu. Signed-off-by: Prakash Sangappa --- include/linux/sched.h | 2 ++ include/uapi/linux/rseq.h | 10 ++++++++++ kernel/rseq.c | 19 +++++++++++++++++++ kernel/sched/core.c | 3 +-- 4 files changed, 32 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 9b4670d85131..0a6d564d2745 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2252,12 +2252,14 @@ unsigned long sched_cpu_util(int cpu); extern bool rseq_delay_resched(void); extern void rseq_delay_resched_fini(void); extern void rseq_delay_resched_tick(void); +extern void rseq_delay_schedule(struct task_struct *tsk); =20 #else =20 static inline bool rseq_delay_resched(void) { return false; } static inline void rseq_delay_resched_fini(void) { } static inline void rseq_delay_resched_tick(void) { } +static inline void rseq_delay_schedule(struct task_struct *tsk) { } =20 #endif =20 diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h index 25fc636b17d5..f4813d931387 100644 --- a/include/uapi/linux/rseq.h +++ b/include/uapi/linux/rseq.h @@ -27,6 +27,7 @@ enum rseq_cs_flags_bit { RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT =3D 1, RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT =3D 2, RSEQ_CS_FLAG_DELAY_RESCHED_BIT =3D 3, + RSEQ_CS_FLAG_RESCHEDULED_BIT =3D 4, }; =20 enum rseq_cs_flags { @@ -38,6 +39,9 @@ enum rseq_cs_flags { (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT), RSEQ_CS_FLAG_DELAY_RESCHED =3D (1U << RSEQ_CS_FLAG_DELAY_RESCHED_BIT), + RSEQ_CS_FLAG_RESCHEDULED =3D + (1U << RSEQ_CS_FLAG_RESCHEDULED_BIT), + }; =20 /* @@ -135,6 +139,12 @@ struct rseq { * Request by user thread to delay preemption. With use * of a timer, kernel grants extra cpu time upto 30us for this * thread before being rescheduled. + * - RSEQ_CS_FLAG_RESCHEDULED + * Set by kernel if the thread was rescheduled in the extra time + * granted due to request RSEQ_CS_DELAY_RESCHED. This bit is + * checked by the thread before calling sched_yield() to yield + * cpu. User thread sets this bit to 0, when setting + * RSEQ_CS_DELAY_RESCHED to request preemption delay. */ __u32 flags; =20 diff --git a/kernel/rseq.c b/kernel/rseq.c index dba44ca9f624..eb20622634ef 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -504,6 +504,25 @@ void rseq_delay_resched_tick(void) #endif } =20 +void rseq_delay_schedule(struct task_struct *tsk) +{ +#ifdef CONFIG_SCHED_HRTICK + u32 flags; + + if (tsk->sched_time_delay) { + tsk->sched_time_delay =3D 0; + if (!tsk->rseq) + return; + if (copy_from_user_nofault(&flags, &tsk->rseq->flags, + sizeof(flags))) + return; + flags |=3D RSEQ_CS_FLAG_RESCHEDULED; + copy_to_user_nofault(&tsk->rseq->flags, &flags, + sizeof(flags)); + } +#endif +} + #ifdef CONFIG_DEBUG_RSEQ =20 /* diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c1b64879115f..e163822d5381 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6752,8 +6752,7 @@ static void __sched notrace __schedule(int sched_mode) picked: clear_tsk_need_resched(prev); clear_preempt_need_resched(); - if (IS_ENABLED(CONFIG_RSEQ)) - prev->sched_time_delay =3D 0; + rseq_delay_schedule(prev); rq->last_seen_need_resched_ns =3D 0; =20 is_switch =3D prev !=3D next; --=20 2.43.5