linux-kernel - [PATCH 2/8] sched_ext: Remove SCX_OPS

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Message-ID: <20240923190020.1446325-3-tj@kernel.org>
Date: Mon, 23 Sep 2024 08:59:29 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com
Cc: kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	sched-ext@...a.com,
	aboorvad@...ux.ibm.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/8] sched_ext: Remove SCX_OPS_PREPPING

The distinction between SCX_OPS_PREPPING and SCX_OPS_ENABLING is not used
anywhere and only adds confusion. Drop SCX_OPS_PREPPING.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 95ed822fa563..2422b2abee6e 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -778,7 +778,6 @@ enum scx_tg_flags {
 };
 
 enum scx_ops_enable_state {
-	SCX_OPS_PREPPING,
 	SCX_OPS_ENABLING,
 	SCX_OPS_ENABLED,
 	SCX_OPS_DISABLING,
@@ -786,7 +785,6 @@ enum scx_ops_enable_state {
 };
 
 static const char *scx_ops_enable_state_str[] = {
-	[SCX_OPS_PREPPING]	= "prepping",
 	[SCX_OPS_ENABLING]	= "enabling",
 	[SCX_OPS_ENABLED]	= "enabled",
 	[SCX_OPS_DISABLING]	= "disabling",
@@ -4971,12 +4969,12 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 	}
 
 	/*
-	 * Set scx_ops, transition to PREPPING and clear exit info to arm the
+	 * Set scx_ops, transition to ENABLING and clear exit info to arm the
 	 * disable path. Failure triggers full disabling from here on.
 	 */
 	scx_ops = *ops;
 
-	WARN_ON_ONCE(scx_ops_set_enable_state(SCX_OPS_PREPPING) !=
+	WARN_ON_ONCE(scx_ops_set_enable_state(SCX_OPS_ENABLING) !=
 		     SCX_OPS_DISABLED);
 
 	atomic_set(&scx_exit_kind, SCX_EXIT_NONE);
@@ -5129,23 +5127,6 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 	 */
 	preempt_disable();
 
-	/*
-	 * From here on, the disable path must assume that tasks have ops
-	 * enabled and need to be recovered.
-	 *
-	 * Transition to ENABLING fails iff the BPF scheduler has already
-	 * triggered scx_bpf_error(). Returning an error code here would lose
-	 * the recorded error information. Exit indicating success so that the
-	 * error is notified through ops.exit() with all the details.
-	 */
-	if (!scx_ops_tryset_enable_state(SCX_OPS_ENABLING, SCX_OPS_PREPPING)) {
-		preempt_enable();
-		spin_unlock_irq(&scx_tasks_lock);
-		WARN_ON_ONCE(atomic_read(&scx_exit_kind) == SCX_EXIT_NONE);
-		ret = 0;
-		goto err_disable_unlock_all;
-	}
-
 	/*
 	 * We're fully committed and can't fail. The PREPPED -> ENABLED
 	 * transitions here are synchronized against sched_ext_free() through
@@ -5176,7 +5157,11 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 	cpus_read_unlock();
 	percpu_up_write(&scx_fork_rwsem);
 
-	/* see above ENABLING transition for the explanation on exiting with 0 */
+	/*
+	 * Returning an error code here would lose the recorded error
+	 * information. Exit indicating success so that the error is notified
+	 * through ops.exit() with all the details.
+	 */
 	if (!scx_ops_tryset_enable_state(SCX_OPS_ENABLED, SCX_OPS_ENABLING)) {
 		WARN_ON_ONCE(atomic_read(&scx_exit_kind) == SCX_EXIT_NONE);
 		ret = 0;
-- 
2.46.0