Re: [PATCH 3/5] tracing/events: add rcu locking around trace eventprints

From: Steven Rostedt
Date: Wed May 06 2009 - 22:10:45 EST



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@xxxxxxxxxx>
>
> 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@xxxxxxx>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
> 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; \
> \
> --
> 1.6.2.1
>
> --
>
--
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