[RFC PATCH v1 1/9] freezer: Introduce freeze_priority field in task_struct

[Zihuan Zhang <zhangzihuan@kylinos.cn>]

To improve the flexibility and correctness of the freezer subsystem,
we introduce a new field `freeze_priority` in `task_struct`.

This field will allow us to assign different freezing priorities to
tasks, enabling prioritized traversal in future changes. This is
particularly useful when dealing with complex inter-process dependencies
in modern userspace workloads (e.g., service managers, IPC daemons).

Although this patch does not change behavior yet, it provides the
necessary infrastructure for upcoming logic to address issues like
dependency stalls and D-state hangs. It also helps avoid potential
race conditions by paving the way for deterministic freezing order.

Signed-off-by: Zihuan Zhang <zhangzihuan@kylinos.cn>
---
 include/linux/freezer.h | 7 +++++++
 include/linux/sched.h   | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index b303472255be..6314f8b68035 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -16,6 +16,13 @@ DECLARE_STATIC_KEY_FALSE(freezer_active);
 extern bool pm_freezing;		/* PM freezing in effect */
 extern bool pm_nosig_freezing;		/* PM nosig freezing in effect */
 
+enum freeze_priority {
+	FREEZE_PRIORITY_HIGH		= 0,
+	FREEZE_PRIORITY_NORMAL		= 1,
+	FREEZE_PRIORITY_LOW		= 2,
+	FREEZE_PRIORITY_NEVER		= 4
+};
+
 /*
  * Timeout for stopping processes
  */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2b272382673d..7915e6214e50 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -910,6 +910,9 @@ struct task_struct {
 	unsigned int			btrace_seq;
 #endif
 
+#ifdef CONFIG_FREEZER
+	unsigned int			freeze_priority;
+#endif
 	unsigned int			policy;
 	unsigned long			max_allowed_capacity;
 	int				nr_cpus_allowed;
-- 
2.25.1