[RFC v2 02/35] RPAL: add struct rpal_service

[Bo Li <libo.gcs85@bytedance.com>]

Each process that uses RPAL features is called an RPAL service.

This patch adds the RPAL header file rpal.h and defines the rpal_service
structure. The struct rpal_service uses a dedicated kmem_cache for
allocation and deallocation, and atomic variables to maintain references
to the struct rpal_service. Additionally, the patch introduces the
rpal_get_service() and rpal_put_service() interfaces to manage reference
counts.

Signed-off-by: Bo Li <libo.gcs85@bytedance.com>
---
 arch/x86/rpal/Makefile   |  5 ++++
 arch/x86/rpal/core.c     | 32 +++++++++++++++++++++++
 arch/x86/rpal/internal.h | 13 ++++++++++
 arch/x86/rpal/service.c  | 56 ++++++++++++++++++++++++++++++++++++++++
 include/linux/rpal.h     | 43 ++++++++++++++++++++++++++++++
 5 files changed, 149 insertions(+)
 create mode 100644 arch/x86/rpal/core.c
 create mode 100644 arch/x86/rpal/internal.h
 create mode 100644 arch/x86/rpal/service.c
 create mode 100644 include/linux/rpal.h

diff --git a/arch/x86/rpal/Makefile b/arch/x86/rpal/Makefile
index e69de29bb2d1..ee3698b5a9b3 100644
--- a/arch/x86/rpal/Makefile
+++ b/arch/x86/rpal/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_RPAL)		+= rpal.o
+
+rpal-y := service.o core.o
diff --git a/arch/x86/rpal/core.c b/arch/x86/rpal/core.c
new file mode 100644
index 000000000000..495dbc1b1536
--- /dev/null
+++ b/arch/x86/rpal/core.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RPAL service level operations
+ * Copyright (c) 2025, ByteDance. All rights reserved.
+ *
+ *     Author: Jiadong Sun <sunjiadong.lff@bytedance.com>
+ */
+
+#include <linux/rpal.h>
+
+#include "internal.h"
+
+int __init rpal_init(void);
+
+bool rpal_inited;
+
+int __init rpal_init(void)
+{
+	int ret = 0;
+
+	ret = rpal_service_init();
+	if (ret)
+		goto fail;
+
+	rpal_inited = true;
+	return 0;
+
+fail:
+	rpal_err("rpal init fail\n");
+	return -1;
+}
+subsys_initcall(rpal_init);
diff --git a/arch/x86/rpal/internal.h b/arch/x86/rpal/internal.h
new file mode 100644
index 000000000000..e44e6fc79677
--- /dev/null
+++ b/arch/x86/rpal/internal.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RPAL service level operations
+ * Copyright (c) 2025, ByteDance. All rights reserved.
+ *
+ *     Author: Jiadong Sun <sunjiadong.lff@bytedance.com>
+ */
+
+extern bool rpal_inited;
+
+/* service.c */
+int __init rpal_service_init(void);
+void __init rpal_service_exit(void);
diff --git a/arch/x86/rpal/service.c b/arch/x86/rpal/service.c
new file mode 100644
index 000000000000..c8e609798d4f
--- /dev/null
+++ b/arch/x86/rpal/service.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RPAL service level operations
+ * Copyright (c) 2025, ByteDance. All rights reserved.
+ *
+ *     Author: Jiadong Sun <sunjiadong.lff@bytedance.com>
+ */
+
+#include <linux/rpal.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static struct kmem_cache *service_cache;
+
+static void __rpal_put_service(struct rpal_service *rs)
+{
+	kmem_cache_free(service_cache, rs);
+}
+
+struct rpal_service *rpal_get_service(struct rpal_service *rs)
+{
+	if (!rs)
+		return NULL;
+	atomic_inc(&rs->refcnt);
+	return rs;
+}
+
+void rpal_put_service(struct rpal_service *rs)
+{
+	if (!rs)
+		return;
+
+	if (atomic_dec_and_test(&rs->refcnt))
+		__rpal_put_service(rs);
+}
+
+int __init rpal_service_init(void)
+{
+	service_cache = kmem_cache_create("rpal_service_cache",
+					  sizeof(struct rpal_service), 0,
+					  SLAB_PANIC, NULL);
+	if (!service_cache) {
+		rpal_err("service init fail\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+void __init rpal_service_exit(void)
+{
+	kmem_cache_destroy(service_cache);
+}
diff --git a/include/linux/rpal.h b/include/linux/rpal.h
new file mode 100644
index 000000000000..73468884cc5d
--- /dev/null
+++ b/include/linux/rpal.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RPAL service level operations
+ * Copyright (c) 2025, ByteDance. All rights reserved.
+ *
+ *     Author: Jiadong Sun <sunjiadong.lff@bytedance.com>
+ */
+
+#ifndef _LINUX_RPAL_H
+#define _LINUX_RPAL_H
+
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+
+#define RPAL_ERROR_MSG "rpal error: "
+#define rpal_err(x...) pr_err(RPAL_ERROR_MSG x)
+#define rpal_err_ratelimited(x...) pr_err_ratelimited(RPAL_ERROR_MSG x)
+
+struct rpal_service {
+	/* reference count of this struct */
+	atomic_t refcnt;
+};
+
+/**
+ * @brief get new reference to a rpal service, a corresponding
+ *  rpal_put_service() should be called later by the caller.
+ *
+ * @param rs The struct rpal_service to get.
+ *
+ * @return new reference of struct rpal_service.
+ */
+struct rpal_service *rpal_get_service(struct rpal_service *rs);
+
+/**
+ * @brief put a reference to a rpal service. If the reference count of
+ *  the service turns to be 0, then release its struct rpal_service.
+ *  rpal_put_service() may be used in an atomic context.
+ *
+ * @param rs The struct rpal_service to put.
+ */
+void rpal_put_service(struct rpal_service *rs);
+#endif
-- 
2.20.1