6.12: misc-additions: Revert sched_ext: scx_bpf_dispatch_from_dsq_set…

…_*() are allowed from unlocked context and sched/ext: Remove sched_fork() hack

These commits reportedly break sched_ext
https://lore.kernel.org/lkml/CAHk-=whGd0dfaJNiWSR60HH5iwxqhUZPDWgHCQd446gH2Wu0yQ@mail.gmail.com/

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.12.y&id=09162013082267af54bb39091b523a8daaa28955
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.12.y&id=acf588f9b6fb560e986365c6b175aaf589ef1f2a

Fixes #1041

linux-tkg-patches/6.12/0012-misc-additions.patch

@@ -238,3 +238,68 @@ index a54663f2e2ab9f..7ffad3eb0a0150 100644
  			case IP_VERSION(13, 0, 14):
  			case IP_VERSION(11, 0, 7):
  			case IP_VERSION(11, 0, 11):
+
+From acf588f9b6fb560e986365c6b175aaf589ef1f2a Mon Sep 17 00:00:00 2001
+From: Tejun Heo <tj@kernel.org>
+Date: Sat, 9 Nov 2024 09:40:25 -1000
+Subject: REVERT: sched_ext: scx_bpf_dispatch_from_dsq_set_*() are allowed from
+ unlocked context
+
+[ Upstream commit 72b85bf6a7f6f6c38c39a1e5b04bc1da1bf5016e ]
+
+diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
+index ecb88c52854475..16613631543f18 100644
+--- a/kernel/sched/ext.c
++++ b/kernel/sched/ext.c
+@@ -6473,8 +6473,6 @@ __bpf_kfunc_end_defs();
+
+ BTF_KFUNCS_START(scx_kfunc_ids_unlocked)
+ BTF_ID_FLAGS(func, scx_bpf_create_dsq, KF_SLEEPABLE)
+-BTF_ID_FLAGS(func, scx_bpf_dispatch_from_dsq_set_slice)
+-BTF_ID_FLAGS(func, scx_bpf_dispatch_from_dsq_set_vtime)
+ BTF_ID_FLAGS(func, scx_bpf_dispatch_from_dsq, KF_RCU)
+ BTF_ID_FLAGS(func, scx_bpf_dispatch_vtime_from_dsq, KF_RCU)
+ BTF_KFUNCS_END(scx_kfunc_ids_unlocked)
+-- 
+cgit 1.2.3-korg
+
+From 09162013082267af54bb39091b523a8daaa28955 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Mon, 28 Oct 2024 14:20:35 +0100
+Subject: REVERT: sched/ext: Remove sched_fork() hack
+
+[ Upstream commit 0f0d1b8e5010bfe1feeb4d78d137e41946a5370d ]
+
+diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
+index 1ddbde64a31b4a..2799e7284fff72 100644
+--- a/include/linux/sched/ext.h
++++ b/include/linux/sched/ext.h
+@@ -199,6 +199,7 @@ struct sched_ext_entity {
+ #ifdef CONFIG_EXT_GROUP_SCHED
+ 	struct cgroup		*cgrp_moving_from;
+ #endif
++	/* must be the last field, see init_scx_entity() */
+ 	struct list_head	tasks_node;
+ };
+
+diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
+index 751d73d500e51d..ecb88c52854475 100644
+--- a/kernel/sched/ext.c
++++ b/kernel/sched/ext.c
+@@ -3567,7 +3567,12 @@ static void scx_ops_exit_task(struct task_struct *p)
+
+ void init_scx_entity(struct sched_ext_entity *scx)
+ {
++	/*
++	 * init_idle() calls this function again after fork sequence is
++	 * complete. Don't touch ->tasks_node as it's already linked.
++	 */
++	memset(scx, 0, offsetof(struct sched_ext_entity, tasks_node));
++
+-	memset(scx, 0, sizeof(*scx));
+ 	INIT_LIST_HEAD(&scx->dsq_list.node);
+ 	RB_CLEAR_NODE(&scx->dsq_priq);
+ 	scx->sticky_cpu = -1;
+-- 
+cgit 1.2.3-korg
+