Re: [ltt-dev] [PATCH] Simple LTTng userspace events through debugfs

[Mathieu Desnoyers]

* Ingo Molnar (mingo@xxxxxxx) wrote:
> 
> * Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote:
> 
> > Hi,
> > 
> > I looked at kmemtrace and noticed that the presence of a debugfs 
> > "marker" file, which lets userspace write events into the trace buffers.
> > 
> > So I just did the same with a
> > 
> > /debugfs/ltt/write_event
> 
> you mean similar to ftrace's /debug/tracing/trace_marker ? ;-)
> 

Quite similar, yes :)

Looking at tracing_mark_write(), I am wondering if the fact that it
returns a count including the added \n is an expected side effect ? A
write() returning a count larger than the number of bytes written seems
to be a bit unexpected... But if we remove the \n from the count, then
the case where one write \0 into the event content would end up doing an
endless loop.

Mathieu

> 	Ingo
> 
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Mathieu Desnoyers
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