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DateThu, 7 May 2009 13:32:17 +0200
FromIngo Molnar <>
SubjectRe: [PATCH 3/5] tracing/events: add rcu locking around trace event prints

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Somehow this patch got dropped. I believe Ted's work requires it.
>
> I'm not sure if we need to include rcupdate.h or not to use
> rcu_read_lock. I think it may be fine to include it in ftrace.h.
>
> Jeremy, does this patch effect anything that you are doing?
>
> -- Steve
>
> On Wed, 15 Apr 2009, Steven Rostedt wrote:
>
> > From: Steven Rostedt <srostedt@redhat.com>
> >
> > Some trace events need to have a way to print out data that his
> > allocated, but will be freed later. Using a function that can allocate
> > memory, and free it with call_rcu, can be useful.
> >
> > This patch adds rcu locking around the print part of the TRACE_EVENT
> > macro to facilitate this.
> >
> > Reported-by: Theodore Tso <tytso@mit.edu>
> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> > ---
> > include/trace/ftrace.h | 4 ++++
> > 1 files changed, 4 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> > index 60c5323..6fb06bd 100644
> > --- a/include/trace/ftrace.h
> > +++ b/include/trace/ftrace.h
> > @@ -62,7 +62,9 @@
> > *
> > * field = (typeof(field))entry;
> > *
> > + * rcu_read_lock();
> > * ret = trace_seq_printf(s, <TP_printk> "\n");
> > + * rcu_read_unlock();
> > * if (!ret)
> > * return TRACE_TYPE_PARTIAL_LINE;
> > *
> > @@ -99,7 +101,9 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
> > \
> > field = (typeof(field))entry; \
> > \
> > + rcu_read_lock(); \
> > ret = trace_seq_printf(s, #call ": " print); \
> > + rcu_read_unlock(); \
> > if (!ret) \
> > return TRACE_TYPE_PARTIAL_LINE; \

Hm, this patch adds usage for RCU primitives, but doesnt include
rcupdate.h.

Ingo


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