From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8F6963F823B; Wed, 8 Jul 2026 21:24:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783545893; cv=none; b=BjV1EypXgSTCHNEWpwTcXb6pLAmxWP1v2x1ADV0xuCcURTZjG9XqQgkJxIbDfoUy80w/ItreWU4K/SCumru6W0qi7glIn8BzG5v/SjQclWQuOb4B6L2GZG1Z6P3Rk0i8LpHXNMz95izgxr2QW2aXqr3dDBtWHzOoyM/+Bw71G+g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783545893; c=relaxed/simple; bh=ub142xZueG6r9/4oeM2Tl2QTmUSYB1AjIlx2xGTFMZc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=U1RFHgK0FRJ3XVOQqemhOavc1TwTThMaqb12XmVd8OadR6hZeUlvDeK6uWJ4VHbv9nMVrgeaZyRRb1/i8h5IYcOpiZ9A7CJGvMOnlzLw0sswzdwv8Qmwgic+GePDOOP/oc2YGTlE1Biqdf+cBbwiUTMvd+lHR47J2Ot2MnbN5kg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dr6LaaRA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dr6LaaRA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A1A01F00A3A; Wed, 8 Jul 2026 21:24:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783545891; bh=9bm49HgIs0GQnaTOlFuMRW24MRjfiCy+CXMxL8dNKCI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dr6LaaRA/IX31Y/Qs0+GSBMXKPPDq7JIO6gAdvCQyeZ9HHek5iGaeePUJdjqOLsvp d/ksriySeUvycDWTrxXuMQmOQDG9N63Iy4I0GBYBcd/GVk8s+jTAaFOaiZ7oPJkSfh ZrscNWovsdOKbCgCD2oWmyhCy5cKxBxbIekpYQF0hjD0BK5dfynRNpCjD5JVGxjNDn OSML2Id2dtDAvG3P2cYwa54uHmhRCVOsnB04MAXD2Ky4Vws+dpEF4023zSPQRoL0we mm1PEpXV6cZTyNzi7j87VFGBO/399BrSDgEVjE/QsPPFQvQSNf3nBTncS/tq//enwS lfcQ9Rmolj6Lg== From: Tejun Heo To: David Vernet , Andrea Righi , Changwoo Min Cc: sched-ext@lists.linux.dev, Emil Tsalapatis , linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH v4 sched_ext/for-7.3 19/40] sched_ext: Add scx_skip_subtree_pre() Date: Wed, 8 Jul 2026 11:24:08 -1000 Message-ID: <20260708212429.3405787-20-tj@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260708212429.3405787-1-tj@kernel.org> References: <20260708212429.3405787-1-tj@kernel.org> Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Factor the sibling/ancestor portion of scx_next_descendant_pre() out as scx_skip_subtree_pre(), a pre-order walk primitive that skips @pos's subtree, and call it from scx_next_descendant_pre(). Same locking rules as the existing primitive. Used in a follow-up to fast-skip subtrees that have nothing to do during a descendant walk. Signed-off-by: Tejun Heo --- kernel/sched/ext/sub.c | 37 ++++++++++++++++++++++++++++--------- kernel/sched/ext/sub.h | 2 ++ 2 files changed, 30 insertions(+), 9 deletions(-) diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c index 5fe2f79064dc..17ed0d28f383 100644 --- a/kernel/sched/ext/sub.c +++ b/kernel/sched/ext/sub.c @@ -21,6 +21,33 @@ #ifdef CONFIG_EXT_SUB_SCHED +/** + * scx_skip_subtree_pre - Skip @pos's subtree in a pre-order walk + * @pos: current position + * @root: walk root + * + * In a walk started by scx_next_descendant_pre(), continue past @pos's subtree: + * return @pos's next sibling, or the closest ancestor's next sibling, or NULL + * if @pos's subtree is the last under @root. Same locking rules. + */ +struct scx_sched *scx_skip_subtree_pre(struct scx_sched *pos, struct scx_sched *root) +{ + struct scx_sched *next; + + lockdep_assert(lockdep_is_held(&scx_enable_mutex) || + lockdep_is_held(&scx_sched_lock) || + rcu_read_lock_any_held()); + + while (pos != root) { + next = list_next_or_null_rcu(&scx_parent(pos)->children, &pos->sibling, + struct scx_sched, sibling); + if (next) + return next; + pos = scx_parent(pos); + } + return NULL; +} + /** * scx_next_descendant_pre - find the next descendant for pre-order walk * @pos: the current position (%NULL to initiate traversal) @@ -48,15 +75,7 @@ struct scx_sched *scx_next_descendant_pre(struct scx_sched *pos, struct scx_sche return next; /* no child, visit my or the closest ancestor's next sibling */ - while (pos != root) { - next = list_next_or_null_rcu(&scx_parent(pos)->children, &pos->sibling, - struct scx_sched, sibling); - if (next) - return next; - pos = scx_parent(pos); - } - - return NULL; + return scx_skip_subtree_pre(pos, root); } static struct scx_sched *scx_find_sub_sched(u64 cgroup_id) diff --git a/kernel/sched/ext/sub.h b/kernel/sched/ext/sub.h index e936867bc5c5..3d5ad9c36d64 100644 --- a/kernel/sched/ext/sub.h +++ b/kernel/sched/ext/sub.h @@ -15,6 +15,7 @@ #ifdef CONFIG_EXT_SUB_SCHED +struct scx_sched *scx_skip_subtree_pre(struct scx_sched *pos, struct scx_sched *root); struct scx_sched *scx_next_descendant_pre(struct scx_sched *pos, struct scx_sched *root); void scx_set_task_sched(struct task_struct *p, struct scx_sched *sch); struct cgroup *sch_cgroup(struct scx_sched *sch); @@ -30,6 +31,7 @@ s32 scx_alloc_pshards(struct scx_sched *sch); #else /* CONFIG_EXT_SUB_SCHED */ static inline struct scx_sched *scx_next_descendant_pre(struct scx_sched *pos, struct scx_sched *root) { return pos ? NULL : root; } +static inline struct scx_sched *scx_skip_subtree_pre(struct scx_sched *pos, struct scx_sched *root) { return NULL; } static inline void scx_set_task_sched(struct task_struct *p, struct scx_sched *sch) {} static inline struct cgroup *sch_cgroup(struct scx_sched *sch) { return NULL; } static inline void set_cgroup_sched(struct cgroup *cgrp, struct scx_sched *sch) {} -- 2.54.0