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.

Link: https://lkml.kernel.org/r/20250825022947.1596226-4-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
Cc: Anna Schumaker <anna.schumaker@oracle.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joanthan Cameron <Jonathan.Cameron@huawei.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Kees Cook <kees@kernel.org>
Cc: Li Huafei <lihuafei1@huawei.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Luo Gengkun <luogengkun@huaweicloud.com>
Cc: Max Kellermann <max.kellermann@ionos.com>
Cc: Nam Cao <namcao@linutronix.de>
Cc: oushixiong <oushixiong@kylinos.cn>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Qianqiang Liu <qianqiang.liu@163.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Zimemrmann <tzimmermann@suse.de>
Cc: Thorsten Blum <thorsten.blum@linux.dev>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Yunhui Cui <cuiyunhui@bytedance.com>
Cc: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files 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@xmission.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();
 	}
 }