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Date: Sun, 27 Nov 2011 19:04:29 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: rostedt@...dmis.org, fweisbec@...il.com, mingo@...hat.com,
paulus@...ba.org, acme@...stprotocols.net
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH 4/9] ftrace: Add enable/disable ftrace_ops control interface
Adding a way to temporarily enable/disable ftrace_ops.
When there is a ftrace_ops with FTRACE_OPS_FL_CONTROL flag
registered, the ftrace_ops_list_func processing function
is used as ftrace function in order to have all registered
ftrace_ops under control.
Also using jump label not to introduce overhead to current
ftrace_ops_list_func processing.
Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
include/linux/ftrace.h | 12 ++++++++++++
kernel/trace/ftrace.c | 39 +++++++++++++++++++++++++++++----------
2 files changed, 41 insertions(+), 10 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 26eafce..28b59f1 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -35,12 +35,14 @@ enum {
FTRACE_OPS_FL_ENABLED = 1 << 0,
FTRACE_OPS_FL_GLOBAL = 1 << 1,
FTRACE_OPS_FL_DYNAMIC = 1 << 2,
+ FTRACE_OPS_FL_CONTROL = 1 << 3,
};
struct ftrace_ops {
ftrace_func_t func;
struct ftrace_ops *next;
unsigned long flags;
+ atomic_t disabled;
#ifdef CONFIG_DYNAMIC_FTRACE
struct ftrace_hash *notrace_hash;
struct ftrace_hash *filter_hash;
@@ -97,6 +99,16 @@ int register_ftrace_function(struct ftrace_ops *ops);
int unregister_ftrace_function(struct ftrace_ops *ops);
void clear_ftrace_function(void);
+static inline void enable_ftrace_function(struct ftrace_ops *ops)
+{
+ atomic_dec(&ops->disabled);
+}
+
+static inline void disable_ftrace_function(struct ftrace_ops *ops)
+{
+ atomic_inc(&ops->disabled);
+}
+
extern void ftrace_stub(unsigned long a0, unsigned long a1);
#else /* !CONFIG_FUNCTION_TRACER */
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0ca0c0d..e5a9498 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -30,6 +30,7 @@
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/rcupdate.h>
+#include <linux/jump_label.h>
#include <trace/events/sched.h>
@@ -94,6 +95,8 @@ ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
static struct ftrace_ops global_ops;
+static struct jump_label_key ftrace_ops_control;
+
static void
ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip);
@@ -196,17 +199,21 @@ static void update_ftrace_function(void)
update_global_ops();
- /*
- * If we are at the end of the list and this ops is
- * not dynamic, then have the mcount trampoline call
- * the function directly
- */
- if (ftrace_ops_list == &ftrace_list_end ||
- (ftrace_ops_list->next == &ftrace_list_end &&
- !(ftrace_ops_list->flags & FTRACE_OPS_FL_DYNAMIC)))
- func = ftrace_ops_list->func;
- else
+ if (jump_label_enabled(&ftrace_ops_control))
func = ftrace_ops_list_func;
+ else {
+ /*
+ * If we are at the end of the list and this ops is
+ * not dynamic, then have the mcount trampoline call
+ * the function directly
+ */
+ if (ftrace_ops_list == &ftrace_list_end ||
+ (ftrace_ops_list->next == &ftrace_list_end &&
+ !(ftrace_ops_list->flags & FTRACE_OPS_FL_DYNAMIC)))
+ func = ftrace_ops_list->func;
+ else
+ func = ftrace_ops_list_func;
+ }
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
ftrace_trace_function = func;
@@ -280,6 +287,9 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
} else
add_ftrace_ops(&ftrace_ops_list, ops);
+ if (ops->flags & FTRACE_OPS_FL_CONTROL)
+ jump_label_inc(&ftrace_ops_control);
+
if (ftrace_enabled)
update_ftrace_function();
@@ -311,6 +321,9 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
if (ret < 0)
return ret;
+ if (ops->flags & FTRACE_OPS_FL_CONTROL)
+ jump_label_dec(&ftrace_ops_control);
+
if (ftrace_enabled)
update_ftrace_function();
@@ -3577,8 +3590,14 @@ ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip)
preempt_disable_notrace();
op = rcu_dereference_raw(ftrace_ops_list);
while (op != &ftrace_list_end) {
+ if (static_branch(&ftrace_ops_control))
+ if ((op->flags & FTRACE_OPS_FL_CONTROL) &&
+ atomic_read(&op->disabled))
+ goto next;
+
if (ftrace_ops_test(op, ip))
op->func(ip, parent_ip);
+ next:
op = rcu_dereference_raw(op->next);
};
preempt_enable_notrace();
--
1.7.1
--
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