Re: [PATCH v2 3/9] crash_core: use panic_try_start() in crash_kexec()

On 8/29/25 10:30, Qianqiang Liu wrote:

On Mon, Aug 25, 2025 at 10:29:31AM +0800, Jinchao Wang wrote:

quoted

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 <redacted>
---
  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@xmission.com>
   */
  
+#include "linux/panic.h"

Can you change this line of code to #include <linux/panic.h>?

Yes, I will.
Thanks for the feedback.>

quoted

  #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

-- 
Best regards,
Jinchao