linux-kernel - [PATCH 38/46] sched_ext: Convert scx_dump

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Message-ID: <20250920005931.2753828-39-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:59:01 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
	arighi@...dia.com,
	multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	memxor@...il.com,
	bpf@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 38/46] sched_ext: Convert scx_dump_state() spinlock to raw spinlock

The scx_dump_state() function uses a regular spinlock to serialize
access. In a subsequent patch, this function will be called while
holding scx_sched_lock, which is a raw spinlock, creating a lock
nesting violation.

Convert the dump_lock to a raw spinlock and use the guard macro for
cleaner lock management.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 4dc82afb7016..fafffe3ee812 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4565,7 +4565,7 @@ static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx,
 
 static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 {
-	static DEFINE_SPINLOCK(dump_lock);
+	static DEFINE_RAW_SPINLOCK(dump_lock);
 	static const char trunc_marker[] = "\n\n~~~~ TRUNCATED ~~~~\n";
 	struct scx_sched *sch = scx_root;
 	struct scx_dump_ctx dctx = {
@@ -4577,11 +4577,10 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 	};
 	struct seq_buf s;
 	struct scx_event_stats events;
-	unsigned long flags;
 	char *buf;
 	int cpu;
 
-	spin_lock_irqsave(&dump_lock, flags);
+	guard(raw_spinlock_irqsave)(&dump_lock);
 
 	seq_buf_init(&s, ei->dump, dump_len);
 
@@ -4705,8 +4704,6 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 	if (seq_buf_has_overflowed(&s) && dump_len >= sizeof(trunc_marker))
 		memcpy(ei->dump + dump_len - sizeof(trunc_marker),
 		       trunc_marker, sizeof(trunc_marker));
-
-	spin_unlock_irqrestore(&dump_lock, flags);
 }
 
 static void scx_error_irq_workfn(struct irq_work *irq_work)
-- 
2.51.0