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Subject[RFC PATCH 07/10] ftrace: Make the function hashlist concurrently usable
Date
Allow the function hashlist to be usable by simultaneous users.
The function tracers can then plug in for their own needs.

This introduces a get/put_function_hlist() that keeps track
of the hashlist users for allocation and release.

We also introduce function_hlist_reset_profile() that resets
the function profiling statistics on a function hashlist already
in use.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/trace/ftrace.c | 5 ++-
kernel/trace/functions_hlist.c | 56 ++++++++++++++++++++++++++++++++++++++-
kernel/trace/functions_hlist.h | 5 ++-
3 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0ded01c..027743c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -490,11 +490,12 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
mutex_lock(&ftrace_profile_lock);
if (ftrace_profile_enabled ^ val) {
if (val) {
- ret = function_hlist_init();
+ ret = get_function_hlist();
if (ret < 0) {
cnt = ret;
goto out;
}
+ function_hlist_reset_profile();

ret = register_ftrace_profiler();
if (ret < 0) {
@@ -509,7 +510,7 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
* so this acts like an synchronize_sched.
*/
unregister_ftrace_profiler();
- function_hlist_release();
+ put_function_hlist();
}
}
out:
diff --git a/kernel/trace/functions_hlist.c b/kernel/trace/functions_hlist.c
index c79c4c5..d682213 100644
--- a/kernel/trace/functions_hlist.c
+++ b/kernel/trace/functions_hlist.c
@@ -20,6 +20,39 @@
DEFINE_PER_CPU(struct func_hlist, func_hlist_cpu);

int functions_hash_bits __read_mostly;
+static atomic_t hlist_refcount;
+
+
+static void function_hlist_reset_profile_cpu(int cpu)
+{
+ struct func_hlist *hlist = &per_cpu(func_hlist_cpu, cpu);
+ struct hlist_head *head;
+ struct hlist_node *node;
+ struct func_node *rec;
+ int i;
+
+ for (i = 0; i < FUNCTIONS_HLIST_SIZE; i++) {
+ head = &hlist->hash[i];
+
+ if (hlist_empty(head))
+ continue;
+
+ hlist_for_each_entry(rec, node, head, node) {
+ rec->counter = 0;
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ rec->time = 0;
+#endif
+ }
+ }
+}
+
+void function_hlist_reset_profile(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu)
+ function_hlist_reset_profile_cpu(cpu);
+}

static void __function_hlist_release(struct func_hlist *hlist)
{
@@ -115,7 +148,7 @@ static int function_hlist_init_cpu(int cpu)
return 0;
}

-void function_hlist_release(void)
+static void function_hlist_release(void)
{
int cpu;
struct func_hlist *hlist;
@@ -126,7 +159,7 @@ void function_hlist_release(void)
}
}

-int function_hlist_init(void)
+static int function_hlist_init(void)
{
int cpu;
int ret = 0;
@@ -140,6 +173,25 @@ int function_hlist_init(void)
return ret;
}

+int get_function_hlist(void)
+{
+ int ret = 0;
+
+ if (atomic_inc_return(&hlist_refcount) == 1) {
+ ret = function_hlist_init();
+ if (ret < 0)
+ atomic_dec(&hlist_refcount);
+ }
+
+ return ret;
+}
+
+void put_function_hlist(void)
+{
+ if (!atomic_dec_return(&hlist_refcount))
+ function_hlist_release();
+}
+
struct func_node *
function_find_hlist_node(struct func_hlist *hlist, unsigned long ip)
{
diff --git a/kernel/trace/functions_hlist.h b/kernel/trace/functions_hlist.h
index 8001f95..a4655c7 100644
--- a/kernel/trace/functions_hlist.h
+++ b/kernel/trace/functions_hlist.h
@@ -35,5 +35,6 @@ function_find_hlist_node(struct func_hlist *hlist, unsigned long ip);
struct func_node *
function_hlist_record_alloc(struct func_hlist *hlist, unsigned long ip);

-int function_hlist_init(void);
-void function_hlist_release(void);
+int get_function_hlist(void);
+void put_function_hlist(void);
+void function_hlist_reset_profile(void);
--
1.6.2.3


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