WIIPdev/hazptr

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

3 files changed, 98 insertions, 0 deletions

diff --git a/include/linux/hazptr.h b/include/linux/hazptr.h
new file mode 100644
index 00000000000000..935eee97c95e6a
--- /dev/null
+++ b/include/linux/hazptr.h
@@ -0,0 +1,48 @@
+#include <linux/list.h>
+
+typedef void* hazptr_t;
+
+#define HAZPTR_UNUSED (1ul)
+
+struct hazptr_context;
+
+struct hazptr_head {
+	struct rcu_head head;
+};
+
+void init_hazptr_context(struct hazptr_context *hzcp);
+hazptr_t *hazptr_alloc(struct hazptr_context *hzcp);
+void hazptr_free(struct hazptr_context *hzcp, hazptr_t *hzp);
+
+#define hazptr_tryprotect(hzp, p, field)	__hazptr_tryprotect(hzp, p, offset_of(__typeof__(*p), field)
+
+static inline bool __hazptr_tryprotect(hazptr_t *hzp, void **p, unsigned long head_offset)
+{
+	void *ptr;
+	struct hazptr_head *head;
+
+	ptr = READ_ONCE(*p);
+
+	if (ptr == NULL)
+		return false;
+	
+	head = (struct hazptr_head *)ptr + head_offset;
+	
+	WRITE_ONCE(*hzp, head);
+	smp_mb();
+
+	ptr = READ_ONCE(*p); // read again
+	
+	if (ptr + head_offset != *hzp) { // pointer changed
+		WRITE_ONCE(*hzp, NULL);  // reset hazard pointer
+		return false;
+	} else
+		return true;
+}
+
+static inline void hazptr_clear(hazptr_t *hzp)
+{
+	WRITE_ONCE(*hzp, NULL);
+}
+
+void call_hazptr(struct hazptr_head *head, rcu_callback_t func);
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 0cfb009a99b9f7..53553aa4622f21 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_RCU_REF_SCALE_TEST) += refscale.o
 obj-$(CONFIG_TREE_RCU) += tree.o
 obj-$(CONFIG_TINY_RCU) += tiny.o
 obj-$(CONFIG_RCU_NEED_SEGCBLIST) += rcu_segcblist.o
+obj-y += hazptr.o
diff --git a/kernel/rcu/hazptr.c b/kernel/rcu/hazptr.c
new file mode 100644
index 00000000000000..9b0e429aebddec
--- /dev/null
+++ b/kernel/rcu/hazptr.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/spinlock.h>
+#include <linux/cleanup.h>
+#include <linux/hazptr.h>
+
+struct hazptr_context {
+	struct list_head list;
+	hazptr_t start_with_one;
+};
+
+struct hazptr_context_list {
+	struct list_head list;
+	spinlock_t lock;
+};
+
+DEFINE_PER_CPU(struct hazptr_context_list, hzc_list);
+
+void init_hazptr_context(struct hazptr_context *hzcp)
+{
+	struct hazptr_context_list *this_hzc_list = this_cpu_ptr(&hzc_list);
+	
+	guard(spinlock)(&this_hzc_list->lock);
+	list_add(&hzcp->list, &this_hzc_list->list);
+}
+
+hazptr_t *hazptr_alloc(struct hazptr_context *hzcp)
+{
+	if (((unsigned long)hzcp->start_with_one) != HAZPTR_UNUSED) {
+		WRITE_ONCE(hzcp->start_with_one, NULL);
+		return &hzcp->start_with_one;
+	}
+
+	return NULL;
+}
+
+void hazptr_free(struct hazptr_context *hzcp, hazptr_t *hzp)
+{
+	WARN_ON(((unsigned long)*hzp) == HAZPTR_UNUSED);
+	WARN_ON(&hzcp->start_with_one != hzp);
+
+	WRITE_ONCE(*hzp, (void *)HAZPTR_UNUSED);
+}
+
+void call_hazptr(struct hazptr_head *head, rcu_callback_t func)
+{
+	head->head.func = func;
+	// TODO
+}