Re: [PATCH v2] printk: add console output tracing

Johannes Berg
2011-11-18T18:46:24Z

On Fri, 2011-11-18 at 19:44 +0100, Frederic Weisbecker wrote:

> > +TRACE_EVENT_CONDITION(console,
> > + TP_PROTO(const char *log_buf, unsigned start, unsigned end,
> > + unsigned log_buf_len),
> > +
> > + TP_ARGS(log_buf, start, end, log_buf_len),
> > +
> > + TP_CONDITION(start != end),
> > +
> > + TP_STRUCT__entry(
> > + __dynamic_array(char, msg,
> > + ((end - start + log_buf_len) &
> > + (log_buf_len - 1)) + 1)
>
> Is all that care about log_buf_len necessary? It seems that
> printk ensures that log_end - con_start never exceeds log_buf_len,
> looking at emit_log_char()

I think it is. The buffer can wrap around so in that case end < start,
which just end-start won't handle here.

johannes