linux-kernel - [PATCH] tracing: use union for multi-usages field

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Date:	Tue, 24 Mar 2009 13:38:06 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Steven Rostedt <srostedt@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] tracing: use union for multi-usages field


Impact: cleanup

cleanup for readability.

struct dyn_ftrace::ip has different usages in his lifecycle,
we use union for it. And also for struct dyn_ftrace::flags.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index db3fed6..cdb0d3f 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -145,9 +145,15 @@ enum {
 };
 
 struct dyn_ftrace {
-	unsigned long		ip; /* address of mcount call-site */
-	unsigned long		flags;
-	struct dyn_arch_ftrace	arch;
+	union {
+		unsigned long		ip; /* address of mcount call-site */
+		struct dyn_ftrace	*freelist;
+	};
+	union {
+		unsigned long		flags;
+		struct dyn_ftrace	*newlist;
+	};
+	struct dyn_arch_ftrace		arch;
 };
 
 int ftrace_force_update(void);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7847806..2c578c5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -339,7 +339,7 @@ static inline int record_frozen(struct dyn_ftrace *rec)
 
 static void ftrace_free_rec(struct dyn_ftrace *rec)
 {
-	rec->ip = (unsigned long)ftrace_free_records;
+	rec->freelist = ftrace_free_records;
 	ftrace_free_records = rec;
 	rec->flags |= FTRACE_FL_FREE;
 }
@@ -377,7 +377,7 @@ static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
 			return NULL;
 		}
 
-		ftrace_free_records = (void *)rec->ip;
+		ftrace_free_records = rec->freelist;
 		memset(rec, 0, sizeof(*rec));
 		return rec;
 	}
@@ -409,7 +409,7 @@ ftrace_record_ip(unsigned long ip)
 		return NULL;
 
 	rec->ip = ip;
-	rec->flags = (unsigned long)ftrace_new_addrs;
+	rec->newlist = ftrace_new_addrs;
 	ftrace_new_addrs = rec;
 
 	return rec;
@@ -729,7 +729,7 @@ static int ftrace_update_code(struct module *mod)
 			return -1;
 
 		p = ftrace_new_addrs;
-		ftrace_new_addrs = (struct dyn_ftrace *)p->flags;
+		ftrace_new_addrs = p->newlist;
 		p->flags = 0L;
 
 		/* convert record (i.e, patch mcount-call with NOP) */


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