Re: [PATCH 1/2] tracing/events: clean up for ftrace_set_clr_event()

[Frederic Weisbecker <fweisbec@gmail.com>]

On Fri, May 08, 2009 at 10:31:42AM +0800, Li Zefan wrote:
> Add a helper function __ftrace_set_clr_event(), and replace some
> ftrace_set_clr_event() calls with this helper, thus we don't need any
> kstrdup() or kmalloc().
> 
> As a side effect, this patch fixes an issue in self tests code, which is
> similar to the one fixed in commit d6bf81ef0f7474434c2a049e8bf3c9146a14dd96
> ("tracing: append ":*" to internal setting of system events")
> 
> It's a small issue and won't cause any bug in fact, but we should do things
> right anyway.
> 
> [ Impact: clean up ]



If this fixes an issue like you described, then it's more than a cleanup :)



> 
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
>  kernel/trace/trace_events.c |  126 ++++++++++++++++---------------------------
>  1 files changed, 46 insertions(+), 80 deletions(-)
> 
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 8d0fae3..45f1099 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -111,11 +111,44 @@ static void ftrace_event_enable_disable(struct ftrace_event_call *call,
>  	}
>  }
>  
> -static int ftrace_set_clr_event(char *buf, int set)
> +/*
> + * __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
> + */
> +static int __ftrace_set_clr_event(const char *match, const char *sub,
> +				  const char *event, int set)
>  {
>  	struct ftrace_event_call *call;
> +	int ret;
> +
> +	mutex_lock(&event_mutex);
> +	list_for_each_entry(call, &ftrace_events, list) {
> +
> +		if (!call->name || !call->regfunc)
> +			continue;
> +
> +		if (match &&
> +		    strcmp(match, call->name) != 0 &&
> +		    strcmp(match, call->system) != 0)
> +			continue;
> +
> +		if (sub && strcmp(sub, call->system) != 0)
> +			continue;
> +
> +		if (event && strcmp(event, call->name) != 0)
> +			continue;


Neat: You can simply use !strcmp(...)


> +
> +		ftrace_event_enable_disable(call, set);
> +
> +		ret = 0;
> +	}
> +	mutex_unlock(&event_mutex);
> +
> +	return ret;
> +}
> +
> +static int ftrace_set_clr_event(char *buf, int set)
> +{
>  	char *event = NULL, *sub = NULL, *match;
> -	int ret = -EINVAL;
>  
>  	/*
>  	 * The buf format can be <subsystem>:<event-name>
> @@ -141,30 +174,7 @@ static int ftrace_set_clr_event(char *buf, int set)
>  			event = NULL;
>  	}
>  
> -	mutex_lock(&event_mutex);
> -	list_for_each_entry(call, &ftrace_events, list) {
> -
> -		if (!call->name || !call->regfunc)
> -			continue;
> -
> -		if (match &&
> -		    strcmp(match, call->name) != 0 &&
> -		    strcmp(match, call->system) != 0)
> -			continue;
> -
> -		if (sub && strcmp(sub, call->system) != 0)
> -			continue;
> -
> -		if (event && strcmp(event, call->name) != 0)
> -			continue;
> -
> -		ftrace_event_enable_disable(call, set);
> -
> -		ret = 0;
> -	}
> -	mutex_unlock(&event_mutex);
> -
> -	return ret;
> +	return __ftrace_set_clr_event(match, sub, event, set);
>  }
>  
>  /* 128 should be much more than enough */
> @@ -408,18 +418,14 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
>  	struct ftrace_event_call *call;
>  	char buf[2];
>  	int set = -1;
> -	int all = 0;
>  	int ret;
>  
> -	if (system[0] == '*')
> -		all = 1;
> -
>  	mutex_lock(&event_mutex);
>  	list_for_each_entry(call, &ftrace_events, list) {
>  		if (!call->name || !call->regfunc)
>  			continue;
>  
> -		if (!all && strcmp(call->system, system) != 0)
> +		if (system && strcmp(call->system, system) != 0)
>  			continue;
>  
>  		/*
> @@ -480,7 +486,6 @@ system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
>  {
>  	const char *system = filp->private_data;
>  	unsigned long val;
> -	char *command;
>  	char buf[64];
>  	ssize_t ret;
>  
> @@ -500,30 +505,16 @@ system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
>  	if (ret < 0)
>  		return ret;
>  
> -	switch (val) {
> -	case 0:
> -	case 1:
> -		break;
> -
> -	default:
> +	if (val != 0 && val != 1)
>  		return -EINVAL;
> -	}
>  
> -	/* +3 for the ":*\0" */
> -	command = kmalloc(strlen(system)+3, GFP_KERNEL);
> -	if (!command)
> -		return -ENOMEM;
> -	sprintf(command, "%s:*", system);
> -
> -	ret = ftrace_set_clr_event(command, val);
> +	ret = __ftrace_set_clr_event(NULL, system, NULL, val);
>  	if (ret)
> -		goto out_free;
> +		goto out;
>  
>  	ret = cnt;
>  
> - out_free:
> -	kfree(command);
> -
> +out:
>  	*ppos += cnt;
>  
>  	return ret;
> @@ -1181,7 +1172,7 @@ static __init int event_trace_init(void)
>  			  &ftrace_show_header_fops);
>  
>  	trace_create_file("enable", 0644, d_events,
> -			  "*", &ftrace_system_enable_fops);
> +			  NULL, &ftrace_system_enable_fops);
>  
>  	for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
>  		/* The linker may leave blanks */
> @@ -1259,7 +1250,6 @@ static __init void event_trace_self_tests(void)
>  {
>  	struct ftrace_event_call *call;
>  	struct event_subsystem *system;
> -	char *sysname;
>  	int ret;
>  
>  	pr_info("Running tests on trace events:\n");
> @@ -1305,14 +1295,7 @@ static __init void event_trace_self_tests(void)
>  
>  		pr_info("Testing event system %s: ", system->name);
>  
> -		/* ftrace_set_clr_event can modify the name passed in. */
> -		sysname = kstrdup(system->name, GFP_KERNEL);
> -		if (WARN_ON(!sysname)) {
> -			pr_warning("Can't allocate memory, giving up!\n");
> -			return;
> -		}
> -		ret = ftrace_set_clr_event(sysname, 1);
> -		kfree(sysname);
> +		ret = __ftrace_set_clr_event(NULL, system->name, NULL, 1);
>  		if (WARN_ON_ONCE(ret)) {
>  			pr_warning("error enabling system %s\n",
>  				   system->name);
> @@ -1321,14 +1304,7 @@ static __init void event_trace_self_tests(void)
>  
>  		event_test_stuff();
>  
> -		sysname = kstrdup(system->name, GFP_KERNEL);
> -		if (WARN_ON(!sysname)) {
> -			pr_warning("Can't allocate memory, giving up!\n");
> -			return;
> -		}
> -		ret = ftrace_set_clr_event(sysname, 0);
> -		kfree(sysname);
> -
> +		ret = __ftrace_set_clr_event(NULL, system->name, NULL, 0);
>  		if (WARN_ON_ONCE(ret))
>  			pr_warning("error disabling system %s\n",
>  				   system->name);
> @@ -1341,15 +1317,8 @@ static __init void event_trace_self_tests(void)
>  	pr_info("Running tests on all trace events:\n");
>  	pr_info("Testing all events: ");
>  
> -	sysname = kmalloc(4, GFP_KERNEL);
> -	if (WARN_ON(!sysname)) {
> -		pr_warning("Can't allocate memory, giving up!\n");
> -		return;
> -	}
> -	memcpy(sysname, "*:*", 4);
> -	ret = ftrace_set_clr_event(sysname, 1);
> +	ret = __ftrace_set_clr_event(NULL, NULL, NULL, 1);
>  	if (WARN_ON_ONCE(ret)) {
> -		kfree(sysname);
>  		pr_warning("error enabling all events\n");
>  		return;
>  	}
> @@ -1357,10 +1326,7 @@ static __init void event_trace_self_tests(void)
>  	event_test_stuff();
>  
>  	/* reset sysname */
> -	memcpy(sysname, "*:*", 4);
> -	ret = ftrace_set_clr_event(sysname, 0);
> -	kfree(sysname);
> -
> +	ret = __ftrace_set_clr_event(NULL, NULL, NULL, 0);
>  	if (WARN_ON_ONCE(ret)) {
>  		pr_warning("error disabling all events\n");
>  		return;
> -- 
> 1.5.4.rc3
> 


I haven't reviewed deeply, but it looks good and bring a rather
good simplification.