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    SubjectRe: [RFC PATCH] ftrace trace event: introduce assignment macros
    On Thu, Dec 09, 2010 at 11:22:11AM -0500, Mathieu Desnoyers wrote:
    > This patch proposes encapsulation of the raw assignments within TP_fast_assign()
    > by introducing tp_assign() and tp_memcpy() macros. This will allow us to:
    >
    > - generically filter from input fields,
    > - redefine the field write primitives.
    >
    > The current macros map directly to the old code. I changed the documentation in
    > tracepoint.txt to reflect these new primitives, but all TRACE_EVENT() users
    > should gradually update their code to use these macro wrappers rather than raw
    > "=" assignments or mempcy() calls.
    >
    > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    > CC: Steven Rostedt <rostedt@goodmis.org>
    > CC: Frederic Weisbecker <fweisbec@gmail.com>
    > CC: Ingo Molnar <mingo@redhat.com>
    > CC: Li Zefan <lizf@cn.fujitsu.com>
    > CC: William Cohen <wcohen@redhat.com>
    > CC: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
    > CC: Theodore Ts'o <tytso@mit.edu>
    > CC: Jason Baron <jbaron@redhat.com>
    > CC: Mel Gorman <mel@csn.ul.ie>
    > CC: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
    > CC: Marcelo Tosatti <mtosatti@redhat.com>
    > CC: Avi Kivity <avi@redhat.com>
    > CC: Gleb Natapov <gleb@redhat.com>
    > CC: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    > CC: Neil Horman <nhorman@tuxdriver.com>
    > CC: Arjan van de Ven <arjan@linux.intel.com>
    > CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > CC: Kei Tokunaga <tokunaga.keiich@jp.fujitsu.com>
    > CC: Martin K. Petersen <martin.petersen@oracle.com>
    > CC: Oleg Nesterov <oleg@redhat.com>
    > CC: Masami Hiramatsu <mhiramat@redhat.com>
    > CC: Josh Stone <jistone@redhat.com>
    > CC: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    > CC: Thomas Gleixner <tglx@linutronix.de>
    > CC: Zhaolei <zhaolei@cn.fujitsu.com>
    > CC: Anton Blanchard <anton@samba.org>
    > ---
    > include/linux/tracepoint.h | 12 ++++++------
    > include/trace/ftrace.h | 6 ++++++
    > 2 files changed, 12 insertions(+), 6 deletions(-)
    >
    > Index: linux-2.6-lttng.git/include/trace/ftrace.h
    > ===================================================================
    > --- linux-2.6-lttng.git.orig/include/trace/ftrace.h
    > +++ linux-2.6-lttng.git/include/trace/ftrace.h
    > @@ -1,4 +1,10 @@
    > /*
    > + * Macros mapping tp_assign() and tp_memcpy() to "=" and memcpy.
    > + */
    > +#define tp_assign(dest, src) __entry->dest = src
    > +#define tp_memcpy(dest, src, len) memcpy(__entry->dest, src, len)

    Looks good.


    > +
    > +/*
    > * Stage 1 of the trace events.
    > *
    > * Override the macros in <trace/trace_events.h> to include the following:
    > Index: linux-2.6-lttng.git/include/linux/tracepoint.h
    > ===================================================================
    > --- linux-2.6-lttng.git.orig/include/linux/tracepoint.h
    > +++ linux-2.6-lttng.git/include/linux/tracepoint.h
    > @@ -306,12 +306,12 @@ static inline void tracepoint_update_pro
    > * *
    > *
    > * TP_fast_assign(
    > - * memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
    > - * __entry->prev_pid = prev->pid;
    > - * __entry->prev_prio = prev->prio;
    > - * memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
    > - * __entry->next_pid = next->pid;
    > - * __entry->next_prio = next->prio;
    > + * tp_memcpy(next_comm, next->comm, TASK_COMM_LEN);
    > + * tp_assign(prev_pid, prev->pid);
    > + * tp_assign(prev_prio, prev->prio);
    > + * tp_memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
    > + * tp_assign(next_pid, next->pid);
    > + * tp_assign(next_prio, next->prio);
    > * )
    > *
    > * *
    >
    > --
    > Mathieu Desnoyers
    > Operating System Efficiency R&D Consultant
    > EfficiOS Inc.
    > http://www.efficios.com


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