Messages in this thread | | | Date | Fri, 18 Nov 2011 19:54:56 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH v2] printk: add console output tracing |
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On Fri, Nov 18, 2011 at 07:46:15PM +0100, Johannes Berg wrote: > 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.
Even if it wraps, end - start should always give a positive result.
We have that check in call_console_drivers():
BUG_ON(((int)(start - end)) > 0)
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