[PATCH v3 1/2] panic: Allow for dynamic custom behavior after panic

[carlos.bilbao@kernel.org]

From: Carlos Bilbao <carlos.bilbao@kernel.org>

Introduce panic_set_handling() to allow overriding the default post-panic
behavior with a priority-based mechanism.

Signed-off-by: Carlos Bilbao (DigitalOcean) <carlos.bilbao@kernel.org>
Reviewed-by: Jan Glauber (DigitalOcean) <jan.glauber@gmail.com>
---
 include/linux/panic.h |  2 ++
 kernel/panic.c        | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/panic.h b/include/linux/panic.h
index 2494d51707ef..cf8d4a944407 100644
--- a/include/linux/panic.h
+++ b/include/linux/panic.h
@@ -98,4 +98,6 @@ extern void add_taint(unsigned flag, enum lockdep_ok);
 extern int test_taint(unsigned flag);
 extern unsigned long get_taint(void);
 
+void panic_set_handling(void (*fn)(void), int priority);
+
 #endif	/* _LINUX_PANIC_H */
diff --git a/kernel/panic.c b/kernel/panic.c
index a3889f38153d..559304546f2e 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -276,6 +276,25 @@ static void panic_other_cpus_shutdown(bool crash_kexec)
 		crash_smp_send_stop();
 }
 
+/*
+ * If set, this function is called after a kernel panic is handled. It can
+ * be assigned using panic_set_handling(), which supports priority-based
+ * logic. For example, specific architectures may provide a default handler
+ * (priority 0) that halts the system to conserve CPU resources.
+ */
+static void (*panic_halt)(void);
+
+static int panic_halt_priority;
+
+void panic_set_handling(void (*fn)(void), int priority)
+{
+	if (panic_halt && priority <= panic_halt_priority)
+		return;
+
+	panic_halt_priority = priority;
+	panic_halt = fn;
+}
+
 /**
  *	panic - halt the system
  *	@fmt: The text string to print
@@ -467,6 +486,9 @@ void panic(const char *fmt, ...)
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 	nbcon_atomic_flush_unsafe();
 
+	if (panic_halt)
+		panic_halt();
+
 	local_irq_enable();
 	for (i = 0; ; i += PANIC_TIMER_STEP) {
 		touch_softlockup_watchdog();
-- 
2.47.1