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Date: Thu, 09 May 2013 13:08:32 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: linux-kernel@...r.kernel.org,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@...il.com>,
yrl.pp-manager.tt@...achi.com, Oleg Nesterov <oleg@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Tom Zanussi <tom.zanussi@...el.com>
Subject: Re: [PATCH 02/11] [BUGFIX] ftrace, kprobes: Fix a deadlock on
ftrace_regex_lock
On Thu, 2013-05-09 at 12:34 -0400, Steven Rostedt wrote:
> On Thu, 2013-05-09 at 12:27 -0400, Steven Rostedt wrote:
>
> > We probably should have a better way to initialize this. As there are 26
> > ftrace_ops currently in the kernel (and this patch doesn't cover all of
> > them). Maybe have the first time its registered to initialize it.
>
> Crap, but it can be used before that. Hmm, I guess all ftrace functions
> will need to check that flag first. We do something similar for rt_mutex
> in -rt.
I added this on top of your patch. I kept the INIT_REGEX_LOCK as it's
only local to ftrace.c and wont spread further. Also, the
ftrace_list_end ftrace_ops is just a place holder (needed for race
conditions that can have function tracers call its stub), so it does not
need to be initialized. If anything tries to grab its mutex, that's a
bug anyway.
What do you think?
-- Steve
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 4ba3a6e..99d0fbc 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -90,6 +90,8 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
* not set this, then the ftrace infrastructure will add recursion
* protection for the caller.
* STUB - The ftrace_ops is just a place holder.
+ * INITIALIZED - The ftrace_ops has already been initialized (first use time
+ * register_ftrace_function() is called, it will initialized the ops)
*/
enum {
FTRACE_OPS_FL_ENABLED = 1 << 0,
@@ -100,6 +102,7 @@ enum {
FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED = 1 << 5,
FTRACE_OPS_FL_RECURSION_SAFE = 1 << 6,
FTRACE_OPS_FL_STUB = 1 << 7,
+ FTRACE_OPS_FL_INITIALIZED = 1 << 8,
};
struct ftrace_ops {
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 7f307e8..3fed7f0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -934,7 +934,6 @@ static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
.func = kprobe_ftrace_handler,
.flags = FTRACE_OPS_FL_SAVE_REGS,
- .regex_lock = __MUTEX_INITIALIZER(kprobe_ftrace_ops.regex_lock),
};
static int kprobe_ftrace_enabled;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ec83928..827f2fe 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -74,7 +74,6 @@
static struct ftrace_ops ftrace_list_end __read_mostly = {
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_STUB,
- INIT_REGEX_LOCK(ftrace_list_end)
};
/* ftrace_enabled is a method to turn ftrace on or off */
@@ -139,6 +138,16 @@ static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
while (likely(op = rcu_dereference_raw((op)->next)) && \
unlikely((op) != &ftrace_list_end))
+static inline void ftrace_ops_init(struct ftrace_ops *ops)
+{
+#ifdef CONFIG_DYNAMIC_FTRACE
+ if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED)) {
+ mutex_init(&ops->regex_lock);
+ ops->flags |= FTRACE_OPS_FL_INITIALIZED;
+ }
+#endif
+}
+
/**
* ftrace_nr_registered_ops - return number of ops registered
*
@@ -915,7 +924,7 @@ static void unregister_ftrace_profiler(void)
#else
static struct ftrace_ops ftrace_profile_ops __read_mostly = {
.func = function_profile_call,
- .flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
INIT_REGEX_LOCK(ftrace_profile_ops)
};
@@ -1112,7 +1121,7 @@ static struct ftrace_ops global_ops = {
.func = ftrace_stub,
.notrace_hash = EMPTY_HASH,
.filter_hash = EMPTY_HASH,
- .flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
INIT_REGEX_LOCK(global_ops)
};
@@ -1255,6 +1264,7 @@ static void free_ftrace_hash_rcu(struct ftrace_hash *hash)
void ftrace_free_filter(struct ftrace_ops *ops)
{
+ ftrace_ops_init(ops);
free_ftrace_hash(ops->filter_hash);
free_ftrace_hash(ops->notrace_hash);
}
@@ -2632,6 +2642,8 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
struct ftrace_hash *hash;
int ret = 0;
+ ftrace_ops_init(ops);
+
if (unlikely(ftrace_disabled))
return -ENODEV;
@@ -2918,6 +2930,7 @@ static void function_trace_probe_call(unsigned long ip, unsigned long parent_ip,
static struct ftrace_ops trace_probe_ops __read_mostly =
{
.func = function_trace_probe_call,
+ .flags = FTRACE_OPS_FL_INITIALIZED,
INIT_REGEX_LOCK(trace_probe_ops)
};
@@ -3401,6 +3414,7 @@ ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove,
int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
int remove, int reset)
{
+ ftrace_ops_init(ops);
return ftrace_set_addr(ops, ip, remove, reset, 1);
}
EXPORT_SYMBOL_GPL(ftrace_set_filter_ip);
@@ -3425,6 +3439,7 @@ ftrace_set_regex(struct ftrace_ops *ops, unsigned char *buf, int len,
int ftrace_set_filter(struct ftrace_ops *ops, unsigned char *buf,
int len, int reset)
{
+ ftrace_ops_init(ops);
return ftrace_set_regex(ops, buf, len, reset, 1);
}
EXPORT_SYMBOL_GPL(ftrace_set_filter);
@@ -3443,6 +3458,7 @@ EXPORT_SYMBOL_GPL(ftrace_set_filter);
int ftrace_set_notrace(struct ftrace_ops *ops, unsigned char *buf,
int len, int reset)
{
+ ftrace_ops_init(ops);
return ftrace_set_regex(ops, buf, len, reset, 0);
}
EXPORT_SYMBOL_GPL(ftrace_set_notrace);
@@ -3533,6 +3549,8 @@ ftrace_set_early_filter(struct ftrace_ops *ops, char *buf, int enable)
{
char *func;
+ ftrace_ops_init(ops);
+
while (buf) {
func = strsep(&buf, ",");
ftrace_set_regex(ops, func, strlen(func), 0, enable);
@@ -4135,7 +4153,7 @@ void __init ftrace_init(void)
static struct ftrace_ops global_ops = {
.func = ftrace_stub,
- .flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
INIT_REGEX_LOCK(global_ops)
};
@@ -4190,8 +4208,8 @@ ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip,
}
static struct ftrace_ops control_ops = {
- .func = ftrace_ops_control_func,
- .flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ .func = ftrace_ops_control_func,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
INIT_REGEX_LOCK(control_ops)
};
@@ -4550,6 +4568,8 @@ int register_ftrace_function(struct ftrace_ops *ops)
{
int ret = -1;
+ ftrace_ops_init(ops);
+
mutex_lock(&ftrace_lock);
ret = __register_ftrace_function(ops);
--
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