linux-kernel - [PATCH 3/9] crash_core: use panic_try_start() in crash

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Message-ID: <20250820091702.512524-4-wangjinchao600@gmail.com>
Date: Wed, 20 Aug 2025 17:14:48 +0800
From: Jinchao Wang <wangjinchao600@...il.com>
To: pmladek@...e.com,
	akpm@...ux-foundation.org,
	Baoquan He <bhe@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Dave Young <dyoung@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	feng.tang@...ux.alibaba.com,
	joel.granados@...nel.org,
	john.ogness@...utronix.de,
	wangjinchao600@...il.com,
	namcao@...utronix.de,
	sravankumarlpu@...il.com,
	kexec@...ts.infradead.org
Subject: [PATCH 3/9] crash_core: use panic_try_start() in crash_kexec()

crash_kexec() had its own code to exclude
parallel execution by setting panic_cpu.
This is already handled by panic_try_start().

Switch to panic_try_start() to remove the
duplication and keep the logic consistent.

Signed-off-by: Jinchao Wang <wangjinchao600@...il.com>
---
 kernel/crash_core.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index a4ef79591eb2..bb38bbaf3a26 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@...ssion.com>
  */
 
+#include "linux/panic.h"
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/buildid.h>
@@ -143,17 +144,7 @@ STACK_FRAME_NON_STANDARD(__crash_kexec);
 
 __bpf_kfunc void crash_kexec(struct pt_regs *regs)
 {
-	int old_cpu, this_cpu;
-
-	/*
-	 * Only one CPU is allowed to execute the crash_kexec() code as with
-	 * panic().  Otherwise parallel calls of panic() and crash_kexec()
-	 * may stop each other.  To exclude them, we use panic_cpu here too.
-	 */
-	old_cpu = PANIC_CPU_INVALID;
-	this_cpu = raw_smp_processor_id();
-
-	if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) {
+	if (panic_try_start()) {
 		/* This is the 1st CPU which comes here, so go ahead. */
 		__crash_kexec(regs);
 
@@ -161,7 +152,7 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs)
 		 * Reset panic_cpu to allow another panic()/crash_kexec()
 		 * call.
 		 */
-		atomic_set(&panic_cpu, PANIC_CPU_INVALID);
+		panic_reset();
 	}
 }
 
-- 
2.43.0