+ panic-use-panic_try_start-in-vpanic.patch added to mm-nonmm-unstable branch

+ panic-use-panic_try_start-in-vpanic.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: panic: use panic_try_start() in vpanic()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     panic-use-panic_try_start-in-vpanic.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/panic-use-panic_try_start-in-vpanic.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jinchao Wang <wangjinchao600@gmail.com>
Subject: panic: use panic_try_start() in vpanic()
Date: Mon, 25 Aug 2025 10:29:33 +0800

vpanic() had open-coded logic to claim panic_cpu with atomic_try_cmpxchg. 
This is already handled by panic_try_start().

Switch to panic_try_start() and use panic_on_other_cpu() for the fallback
path.

This removes duplicate code and makes panic handling consistent across
functions.

Link: https://lkml.kernel.org/r/20250825022947.1596226-6-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>
---

 kernel/panic.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/kernel/panic.c~panic-use-panic_try_start-in-vpanic
+++ a/kernel/panic.c
@@ -420,7 +420,6 @@ void vpanic(const char *fmt, va_list arg
 	static char buf[1024];
 	long i, i_next = 0, len;
 	int state = 0;
-	int old_cpu, this_cpu;
 	bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
 
 	if (panic_on_warn) {
@@ -457,13 +456,10 @@ void vpanic(const char *fmt, va_list arg
 	 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
 	 * panic_cpu to this CPU.  In this case, this is also the 1st CPU.
 	 */
-	old_cpu = PANIC_CPU_INVALID;
-	this_cpu = raw_smp_processor_id();
-
 	/* atomic_try_cmpxchg updates old_cpu on failure */
-	if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) {
+	if (panic_try_start()) {
 		/* go ahead */
-	} else if (old_cpu != this_cpu)
+	} else if (panic_on_other_cpu())
 		panic_smp_self_stop();
 
 	console_verbose();
_

Patches currently in -mm which might be from wangjinchao600@gmail.com are

panic-introduce-helper-functions-for-panic-state.patch
fbdev-use-panic_in_progress-helper.patch
crash_core-use-panic_try_start-in-crash_kexec.patch
panic-use-panic_try_start-in-nmi_panic.patch
panic-use-panic_try_start-in-vpanic.patch
printk-nbcon-use-panic_on_this_cpu-helper.patch
panic-printk-replace-this_cpu_in_panic-with-panic_on_this_cpu.patch
panic-printk-replace-other_cpu_in_panic-with-panic_on_other_cpu.patch
watchdog-skip-checks-when-panic-is-in-progress.patch