linux-kernel - Re: Re: [PATCH v2 2/3] tracing: initialize trace

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Date: Thu, 25 Jan 2024 18:52:07 -0300
From: "Ricardo B. Marliere" <ricardo@...liere.net>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v2 2/3] tracing: initialize trace_seq buffers

Hi Steve,

On 25 Jan 15:44, Steven Rostedt wrote:
> On Thu, 25 Jan 2024 17:16:21 -0300
> "Ricardo B. Marliere" <ricardo@...liere.net> wrote:
> 
> > Now that trace_seq_reset have been created, correct the places where the
> > buffers need to be initialized.
> 
> This patch would need to come first. You don't ever want to intentionally
> create a broken kernel.

Indeed, sorry for the lack of attention.

> 
> Also, the change log should be:
> 
>   In order to extend trace_seq into being dynamic, the struct trace_seq
>   will no longer be valid if simply set to zero. Call trace_seq_init() for
>   all trace_seq when they are first created.

Ack.

> 
> > 
> > Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> > Signed-off-by: Ricardo B. Marliere <ricardo@...liere.net>
> > ---
> >  kernel/trace/trace.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> 
> You also need to initialize iter.seq in ftrace_dump()

Thanks a lot for reviewing, I will send a v3.
-	Ricardo


> 
> -- Steve
> 
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index d4c55d3e21c2..9827700d0164 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -4889,6 +4889,9 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
> >  
> >  	mutex_unlock(&trace_types_lock);
> >  
> > +	trace_seq_init(&iter->seq);
> > +	trace_seq_init(&iter->tmp_seq);
> > +
> >  	return iter;
> >  
> >   fail:
> > @@ -6770,6 +6773,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
> >  	}
> >  
> >  	trace_seq_init(&iter->seq);
> > +	trace_seq_init(&iter->tmp_seq);
> >  	iter->trace = tr->current_trace;
> >  
> >  	if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
> > @@ -6947,6 +6951,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
> >  	trace_iterator_reset(iter);
> >  	cpumask_clear(iter->started);
> >  	trace_seq_init(&iter->seq);
> > +	trace_seq_init(&iter->tmp_seq);
> >  
> >  	trace_event_read_lock();
> >  	trace_access_lock(iter->cpu_file);
> > @@ -8277,6 +8282,9 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
> >  	if (ret < 0)
> >  		trace_array_put(tr);
> >  
> > +	trace_seq_init(&info->iter.seq);
> > +	trace_seq_init(&info->iter.tmp_seq);
> > +
> >  	return ret;
> >  }
> >  
> > @@ -10300,6 +10308,9 @@ void trace_init_global_iter(struct trace_iterator *iter)
> >  	iter->temp_size = STATIC_TEMP_BUF_SIZE;
> >  	iter->fmt = static_fmt_buf;
> >  	iter->fmt_size = STATIC_FMT_BUF_SIZE;
> > +
> > +	trace_seq_init(&iter->seq);
> > +	trace_seq_init(&iter->tmp_seq);
> >  }
> >  
> >  void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
> > @@ -10712,6 +10723,9 @@ void __init early_trace_init(void)
> >  			tracepoint_printk = 0;
> >  		else
> >  			static_key_enable(&tracepoint_printk_key.key);
> > +
> > +		trace_seq_init(&tracepoint_print_iter->seq);
> > +		trace_seq_init(&tracepoint_print_iter->tmp_seq);
> >  	}
> >  	tracer_alloc_buffers();
> >  
>