Fix a deadlock on ftrace_regex_lock which happens when setting
an enable_event trigger on dynamic kprobe event as below.
----
sh-2.05b# echo p vfs_symlink > kprobe_events
sh-2.05b# echo vfs_symlink:enable_event:kprobes:p_vfs_symlink_0 >
set_ftrace_filter
=============================================
[ INFO: possible recursive locking detected ]
3.9.0+ #35 Not tainted
---------------------------------------------
sh/72 is trying to acquire lock:
(ftrace_regex_lock){+.+.+.}, at: [<ffffffff810ba6c1>]
ftrace_set_hash+0x81/0x1f0
but task is already holding lock:
(ftrace_regex_lock){+.+.+.}, at: [<ffffffff810b7cbd>]
ftrace_regex_write.isra.29.part.30+0x3d/0x220
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(ftrace_regex_lock);
lock(ftrace_regex_lock);
*** DEADLOCK ***
----
To fix that, this introduces a finer regex_lock for each ftrace_ops.
ftrace_regex_lock seems that a big lock which protect all
filter/notrace_hash operation, but it doesn't need to be a global
lock after supporting multiple ftrace_ops because each ftrace_ops
has its own filter/notrace_hash.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Frederic Weisbecker <fweis...@gmail.com>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Tom Zanussi <tom.zanu...@intel.com>
---
include/linux/ftrace.h | 1 +
kernel/kprobes.c | 1 +
kernel/trace/ftrace.c | 43 +++++++++++++++++++++++++++----------------
3 files changed, 29 insertions(+), 16 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index f83e17a..4ba3a6e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -110,6 +110,7 @@ struct ftrace_ops {
#ifdef CONFIG_DYNAMIC_FTRACE
struct ftrace_hash *notrace_hash;
struct ftrace_hash *filter_hash;
+ struct mutex regex_lock;
#endif
};
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 3fed7f0..7f307e8 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -934,6 +934,7 @@ 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 8a5c017..3f29b3d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -64,9 +64,17 @@
#define FL_GLOBAL_CONTROL_MASK (FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_CONTROL)
+#ifdef CONFIG_DYNAMIC_FTRACE
+#define INIT_REGEX_LOCK(opsname) \
+ .regex_lock = __MUTEX_INITIALIZER(opsname.regex_lock),
+#else
+#define INIT_REGEX_LOCK(opsname)
+#endif
+
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 */
@@ -908,6 +916,7 @@ static void unregister_ftrace_profiler(void)
static struct ftrace_ops ftrace_profile_ops __read_mostly = {
.func = function_profile_call,
.flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ INIT_REGEX_LOCK(ftrace_profile_ops)
};
static int register_ftrace_profiler(void)
@@ -1104,10 +1113,9 @@ static struct ftrace_ops global_ops = {
.notrace_hash = EMPTY_HASH,
.filter_hash = EMPTY_HASH,
.flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ INIT_REGEX_LOCK(global_ops)
};
-static DEFINE_MUTEX(ftrace_regex_lock);
-
struct ftrace_page {
struct ftrace_page *next;
struct dyn_ftrace *records;
@@ -2656,7 +2664,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
}
}
- mutex_lock(&ftrace_regex_lock);
+ mutex_lock(&ops->regex_lock);
if ((file->f_mode & FMODE_WRITE) &&
(file->f_flags & O_TRUNC))
@@ -2677,7 +2685,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
}
} else
file->private_data = iter;
- mutex_unlock(&ftrace_regex_lock);
+ mutex_unlock(&ops->regex_lock);
return ret;
}
@@ -2910,6 +2918,7 @@ 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,
+ INIT_REGEX_LOCK(trace_probe_ops)
};
static int ftrace_probe_registered;
@@ -3256,18 +3265,18 @@ ftrace_regex_write(struct file *file, const char __user
*ubuf,
if (!cnt)
return 0;
- mutex_lock(&ftrace_regex_lock);
-
- ret = -ENODEV;
- if (unlikely(ftrace_disabled))
- goto out_unlock;
-
if (file->f_mode & FMODE_READ) {
struct seq_file *m = file->private_data;
iter = m->private;
} else
iter = file->private_data;
+ mutex_lock(&iter->ops->regex_lock);
+
+ ret = -ENODEV;
+ if (unlikely(ftrace_disabled))
+ goto out_unlock;
+
parser = &iter->parser;
read = trace_get_user(parser, ubuf, cnt, ppos);
@@ -3282,7 +3291,7 @@ ftrace_regex_write(struct file *file, const char __user
*ubuf,
ret = read;
out_unlock:
- mutex_unlock(&ftrace_regex_lock);
+ mutex_unlock(&iter->ops->regex_lock);
return ret;
}
@@ -3344,7 +3353,7 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char
*buf, int len,
if (!hash)
return -ENOMEM;
- mutex_lock(&ftrace_regex_lock);
+ mutex_lock(&ops->regex_lock);
if (reset)
ftrace_filter_reset(hash);
if (buf && !ftrace_match_records(hash, buf, len)) {
@@ -3366,7 +3375,7 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char
*buf, int len,
mutex_unlock(&ftrace_lock);
out_regex_unlock:
- mutex_unlock(&ftrace_regex_lock);
+ mutex_unlock(&ops->regex_lock);
free_ftrace_hash(hash);
return ret;
@@ -3551,14 +3560,14 @@ int ftrace_regex_release(struct inode *inode, struct
file *file)
int filter_hash;
int ret;
- mutex_lock(&ftrace_regex_lock);
if (file->f_mode & FMODE_READ) {
iter = m->private;
-
seq_release(inode, file);
} else
iter = file->private_data;
+ mutex_lock(&iter->ops->regex_lock);
+
parser = &iter->parser;
if (trace_parser_loaded(parser)) {
parser->buffer[parser->idx] = 0;
@@ -3587,7 +3596,7 @@ int ftrace_regex_release(struct inode *inode, struct file
*file)
free_ftrace_hash(iter->hash);
kfree(iter);
- mutex_unlock(&ftrace_regex_lock);
+ mutex_unlock(&iter->ops->regex_lock);
return 0;
}
@@ -4127,6 +4136,7 @@ void __init ftrace_init(void)
static struct ftrace_ops global_ops = {
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_RECURSION_SAFE,
+ INIT_REGEX_LOCK(global_ops)
};
static int __init ftrace_nodyn_init(void)
@@ -4182,6 +4192,7 @@ 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,
+ INIT_REGEX_LOCK(control_ops)
};
static inline void
--
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