Re: [PATCH 1/3] ftrace: Move setting of clock-source out ofoptions

[Steven Rostedt]

Hi,

I like the series and I'll pull it, but there's one thing that bothers me. 
We should fix it too...


On Tue, 25 Aug 2009, Zhaolei wrote:

> There are many clock source for tracing system but we can only
> enable/disable one bit by trace/options file.
> We can move setting of clock-source out of options and add a separate
> file for it:
>  # cat trace_clock
>  [local] global
>  # echo global > trace_clock
>  # cat trace_clock
>  local [global]
> 
> Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
> ---
>  kernel/trace/trace.c |   92 ++++++++++++++++++++++++++++++++++++++++---------
>  kernel/trace/trace.h |    7 ++--
>  2 files changed, 79 insertions(+), 20 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index b7d873b..5af6f83 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -323,12 +323,21 @@ static const char *trace_options[] = {
>  	"printk-msg-only",
>  	"context-info",
>  	"latency-format",
> -	"global-clock",
>  	"sleep-time",
>  	"graph-time",
>  	NULL
>  };
>  
> +static struct {
> +	u64 (*func)(void);
> +	const char *name;
> +} trace_clocks[] = {
> +	{ trace_clock_local,	"local" },
> +	{ trace_clock_global,	"global" },
> +};
> +
> +int trace_clock_id;
> +
>  /*
>   * ftrace_max_lock is used to protect the swapping of buffers
>   * when taking a max snapshot. The buffers themselves are
> @@ -2159,22 +2168,6 @@ static void set_tracer_flags(unsigned int mask, int enabled)
>  		trace_flags |= mask;
>  	else
>  		trace_flags &= ~mask;
> -
> -	if (mask == TRACE_ITER_GLOBAL_CLK) {
> -		u64 (*func)(void);
> -
> -		if (enabled)
> -			func = trace_clock_global;
> -		else
> -			func = trace_clock_local;
> -
> -		mutex_lock(&trace_types_lock);
> -		ring_buffer_set_clock(global_trace.buffer, func);
> -
> -		if (max_tr.buffer)
> -			ring_buffer_set_clock(max_tr.buffer, func);
> -		mutex_unlock(&trace_types_lock);
> -	}
>  }
>  
>  static ssize_t
> @@ -3142,6 +3135,62 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
>  	return cnt;
>  }
>  
> +static ssize_t tracing_clock_read(struct file *filp, char __user *ubuf,
> +				  size_t cnt, loff_t *ppos)
> +{
> +	char buf[64];

What happens if we add more clocks. Our list can only be 64 bytes long. It 
would be a good idea to change this to do something like the trace_options 
uses. That is, it dynamically allocates buf, by figuring out how much it 
needs. This should do that too.

Thanks,

-- Steve

> +	int bufiter = 0;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(trace_clocks); i++)
> +		bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter,
> +			"%s%s%s%s", i ? " " : "",
> +			i == trace_clock_id ? "[" : "", trace_clocks[i].name,
> +			i == trace_clock_id ? "]" : "");
> +	bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter, "\n");
> +
> +	return simple_read_from_buffer(ubuf, cnt, ppos, buf, bufiter);
> +}
> +
> +static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
> +				   size_t cnt, loff_t *fpos)
> +{
> +	char buf[64];
> +	const char *clockstr;
> +	int i;
> +
> +	if (cnt >= sizeof(buf))
> +		return -EINVAL;
> +
> +	if (copy_from_user(&buf, ubuf, cnt))
> +		return -EFAULT;
> +
> +	buf[cnt] = 0;
> +
> +	clockstr = strstrip(buf);
> +
> +	for (i = 0; i < ARRAY_SIZE(trace_clocks); i++) {
> +		if (strcmp(trace_clocks[i].name, clockstr) == 0)
> +			break;
> +	}
> +	if (i == ARRAY_SIZE(trace_clocks))
> +		return -EINVAL;
> +
> +	trace_clock_id = i;
> +
> +	mutex_lock(&trace_types_lock);
> +
> +	ring_buffer_set_clock(global_trace.buffer, trace_clocks[i].func);
> +	if (max_tr.buffer)
> +		ring_buffer_set_clock(max_tr.buffer, trace_clocks[i].func);
> +
> +	mutex_unlock(&trace_types_lock);
> +
> +	*fpos += cnt;
> +
> +	return cnt;
> +}
> +
>  static const struct file_operations tracing_max_lat_fops = {
>  	.open		= tracing_open_generic,
>  	.read		= tracing_max_lat_read,
> @@ -3179,6 +3228,12 @@ static const struct file_operations tracing_mark_fops = {
>  	.write		= tracing_mark_write,
>  };
>  
> +static const struct file_operations trace_clock_fops = {
> +	.open		= tracing_open_generic,
> +	.read		= tracing_clock_read,
> +	.write		= tracing_clock_write,
> +};
> +
>  struct ftrace_buffer_info {
>  	struct trace_array	*tr;
>  	void			*spare;
> @@ -3910,6 +3965,9 @@ static __init int tracer_init_debugfs(void)
>  	trace_create_file("saved_cmdlines", 0444, d_tracer,
>  			NULL, &tracing_saved_cmdlines_fops);
>  
> +	trace_create_file("trace_clock", 0644, d_tracer, NULL,
> +			  &trace_clock_fops);
> +
>  #ifdef CONFIG_DYNAMIC_FTRACE
>  	trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
>  			&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 606073c..0545c2b 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -586,6 +586,8 @@ trace_vprintk(unsigned long ip, const char *fmt, va_list args);
>  
>  extern unsigned long trace_flags;
>  
> +extern int trace_clock_id;
> +
>  /* Standard output formatting function used for function return traces */
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  extern enum print_line_t print_graph_function(struct trace_iterator *iter);
> @@ -674,9 +676,8 @@ enum trace_iterator_flags {
>  	TRACE_ITER_PRINTK_MSGONLY	= 0x10000,
>  	TRACE_ITER_CONTEXT_INFO		= 0x20000, /* Print pid/cpu/time */
>  	TRACE_ITER_LATENCY_FMT		= 0x40000,
> -	TRACE_ITER_GLOBAL_CLK		= 0x80000,
> -	TRACE_ITER_SLEEP_TIME		= 0x100000,
> -	TRACE_ITER_GRAPH_TIME		= 0x200000,
> +	TRACE_ITER_SLEEP_TIME		= 0x80000,
> +	TRACE_ITER_GRAPH_TIME		= 0x100000,
>  };
>  
>  /*
> -- 
> 1.5.5.3
> 
> 
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