[PATCH] ftrace: Replace ftrace_disabled variable with ftrace_is_dead function

[PATCH] ftrace: Replace ftrace_disabled variable with ftrace_is_dead function

[Bang Li]

Use the existing function ftrace_is_dead to replace the variable to make
the code clearer.

Signed-off-by: Bang Li <libang.li@antgroup.com>
---
 kernel/trace/ftrace.c | 46 +++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 50ca4d4f8840..4a08c79db677 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2693,7 +2693,7 @@ void __weak ftrace_replace_code(int mod_flags)
 	int schedulable = mod_flags & FTRACE_MODIFY_MAY_SLEEP_FL;
 	int failed;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return;
 
 	do_for_each_ftrace_rec(pg, rec) {
@@ -2789,7 +2789,7 @@ ftrace_nop_initialize(struct module *mod, struct dyn_ftrace *rec)
 {
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return 0;
 
 	ret = ftrace_init_nop(mod, rec);
@@ -3014,7 +3014,7 @@ int ftrace_startup(struct ftrace_ops *ops, int command)
 {
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	ret = __register_ftrace_function(ops);
@@ -3054,7 +3054,7 @@ int ftrace_startup(struct ftrace_ops *ops, int command)
 	 * to prevent the NULL pointer, instead of totally rolling it back and
 	 * free trampoline, because those actions could cause further damage.
 	 */
-	if (unlikely(ftrace_disabled)) {
+	if (unlikely(ftrace_is_dead())) {
 		__unregister_ftrace_function(ops);
 		return -ENODEV;
 	}
@@ -3068,7 +3068,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
 {
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	ret = __unregister_ftrace_function(ops);
@@ -3211,7 +3211,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
 		for (i = 0; i < pg->index; i++) {
 
 			/* If something went wrong, bail without enabling anything */
-			if (unlikely(ftrace_disabled))
+			if (unlikely(ftrace_is_dead()))
 				return -1;
 
 			p = &pg->records[i];
@@ -3604,7 +3604,7 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 	loff_t l = *pos; /* t_probe_start() must use original pos */
 	void *ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return NULL;
 
 	if (iter->flags & FTRACE_ITER_PROBE)
@@ -3642,7 +3642,7 @@ static void *t_start(struct seq_file *m, loff_t *pos)
 
 	mutex_lock(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return NULL;
 
 	/*
@@ -3908,7 +3908,7 @@ ftrace_avail_open(struct inode *inode, struct file *file)
 	if (ret)
 		return ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
@@ -3981,7 +3981,7 @@ ftrace_avail_addrs_open(struct inode *inode, struct file *file)
 	if (ret)
 		return ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
@@ -4025,7 +4025,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 
 	ftrace_ops_init(ops);
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	if (tracing_check_open_get_tr(tr))
@@ -4310,7 +4310,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
 
 	mutex_lock(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		goto out_unlock;
 
 	if (func_g.type == MATCH_INDEX) {
@@ -5181,7 +5181,7 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 	} else
 		iter = file->private_data;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	/* iter->hash is a local copy, so we don't need regex_lock */
@@ -5267,7 +5267,7 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
 	struct ftrace_hash *hash;
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	mutex_lock(&ops->func_hash->regex_lock);
@@ -6159,7 +6159,7 @@ ftrace_graph_open(struct inode *inode, struct file *file)
 	struct ftrace_graph_data *fgd;
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	fgd = kmalloc(sizeof(*fgd), GFP_KERNEL);
@@ -6187,7 +6187,7 @@ ftrace_graph_notrace_open(struct inode *inode, struct file *file)
 	struct ftrace_graph_data *fgd;
 	int ret;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return -ENODEV;
 
 	fgd = kmalloc(sizeof(*fgd), GFP_KERNEL);
@@ -6297,7 +6297,7 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 
 	mutex_lock(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled)) {
+	if (unlikely(ftrace_is_dead())) {
 		mutex_unlock(&ftrace_lock);
 		return -ENODEV;
 	}
@@ -6767,7 +6767,7 @@ void ftrace_release_mod(struct module *mod)
 
 	mutex_lock(&ftrace_lock);
 
-	if (ftrace_disabled)
+	if (unlikely(ftrace_is_dead()))
 		goto out_unlock;
 
 	list_for_each_entry_safe(mod_map, n, &ftrace_mod_maps, list) {
@@ -6830,7 +6830,7 @@ void ftrace_module_enable(struct module *mod)
 
 	mutex_lock(&ftrace_lock);
 
-	if (ftrace_disabled)
+	if (unlikely(ftrace_is_dead()))
 		goto out_unlock;
 
 	/*
@@ -6905,7 +6905,7 @@ void ftrace_module_init(struct module *mod)
 {
 	int ret;
 
-	if (ftrace_disabled || !mod->num_ftrace_callsites)
+	if (unlikely(ftrace_is_dead()) || !mod->num_ftrace_callsites)
 		return;
 
 	ret = ftrace_process_locs(mod, mod->ftrace_callsites,
@@ -8171,7 +8171,7 @@ static void ftrace_startup_sysctl(void)
 {
 	int command;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return;
 
 	/* Force update next time */
@@ -8189,7 +8189,7 @@ static void ftrace_shutdown_sysctl(void)
 {
 	int command;
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		return;
 
 	/* ftrace_start_up is true if ftrace is running */
@@ -8225,7 +8225,7 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 	mutex_lock(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled))
+	if (unlikely(ftrace_is_dead()))
 		goto out;
 
 	ret = proc_dointvec(table, write, buffer, lenp, ppos);
-- 
2.19.1.6.gb485710b

Re: [PATCH] ftrace: Replace ftrace_disabled variable with ftrace_is_dead function

[Steven Rostedt]

On Fri, 19 Apr 2024 22:38:44 +0800
"Bang Li" <libang.li@antgroup.com> wrote:

> Use the existing function ftrace_is_dead to replace the variable to make
> the code clearer.
> 
> Signed-off-by: Bang Li <libang.li@antgroup.com>
> ---
>  kernel/trace/ftrace.c | 46 +++++++++++++++++++++----------------------
>  1 file changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 50ca4d4f8840..4a08c79db677 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2693,7 +2693,7 @@ void __weak ftrace_replace_code(int mod_flags)
>  	int schedulable = mod_flags & FTRACE_MODIFY_MAY_SLEEP_FL;
>  	int failed;
>  
> -	if (unlikely(ftrace_disabled))
> +	if (unlikely(ftrace_is_dead()))
>  		return;
>  

NACK!

ftrace_is_dead() is only there to make the static variable
"ftrace_disabled" available for code outside of ftrace.c. In ftrace.c,
it is perfectly fine to use ftrace_disabled.

-- Steve

Re: [PATCH] ftrace: Replace ftrace_disabled variable with ftrace_is_dead function

[Bang Li]

On 2024/4/20 9:40, Steven Rostedt wrote:
> On Fri, 19 Apr 2024 22:38:44 +0800
> "Bang Li" <libang.li@antgroup.com> wrote:
> 
>> Use the existing function ftrace_is_dead to replace the variable to make
>> the code clearer.
>>
>> Signed-off-by: Bang Li <libang.li@antgroup.com>
>> ---
>>   kernel/trace/ftrace.c | 46 +++++++++++++++++++++----------------------
>>   1 file changed, 23 insertions(+), 23 deletions(-)
>>
>> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
>> index 50ca4d4f8840..4a08c79db677 100644
>> --- a/kernel/trace/ftrace.c
>> +++ b/kernel/trace/ftrace.c
>> @@ -2693,7 +2693,7 @@ void __weak ftrace_replace_code(int mod_flags)
>>   	int schedulable = mod_flags & FTRACE_MODIFY_MAY_SLEEP_FL;
>>   	int failed;
>>   
>> -	if (unlikely(ftrace_disabled))
>> +	if (unlikely(ftrace_is_dead()))
>>   		return;
>>   
> 
> NACK!
> 
> ftrace_is_dead() is only there to make the static variable
> "ftrace_disabled" available for code outside of ftrace.c. In ftrace.c,
> it is perfectly fine to use ftrace_disabled.
> 
> -- Steve

Thank you for your explanation, let me understand this. How about
replacing ftrace_disabled with unlike(ftrace_disabled)?

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 50ca4d4f8840..76e0814723cb 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6767,7 +6767,7 @@ void ftrace_release_mod(struct module *mod)

         mutex_lock(&ftrace_lock);

-       if (ftrace_disabled)
+       if (unlikely(ftrace_disabled))
                 goto out_unlock;

         list_for_each_entry_safe(mod_map, n, &ftrace_mod_maps, list) {
@@ -6830,7 +6830,7 @@ void ftrace_module_enable(struct module *mod)

         mutex_lock(&ftrace_lock);

-       if (ftrace_disabled)
+       if (unlikely(ftrace_disabled))
                 goto out_unlock;

         /*

Thanks again for the review!
Bang

Re: [PATCH] ftrace: Replace ftrace_disabled variable with ftrace_is_dead function

[Steven Rostedt]

On Sat, 20 Apr 2024 11:50:29 +0800
"Bang Li" <libang.li@antgroup.com> wrote:

> Thank you for your explanation, let me understand this. How about
> replacing ftrace_disabled with unlike(ftrace_disabled)?

Why? They are slow paths. No need to optimize them.

-- Steve