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SubjectRe: [PATCH 1/1] ftrace: fix dynamic ftrace filter reset issue
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On Wed, 2012-03-21 at 11:22 +0530, Rajesh Bhagat wrote:
> >From 60ec8a88ba671fa0b424f7b4467dba3ea8a2a2c8 Mon Sep 17 00:00:00 2001
> From: Rajesh Bhagat <rajesh.lnx@gmail.com>
> Date: Tue, 20 Mar 2012 10:35:59 +0530
> Subject: [PATCH 1/1] ftrace: fix dynamic ftrace filter reset issue
>
> This patch resets the trace_array using tracing_reset_online_cpus, if same
> tracer is set again instead of just returning from funtion tracing_set_tracer.
>
> problem description
> -------------------
> once function tracer is set, set_ftrace_filter not working.
> /debug/tracing # echo function > current_tracer
> /debug/tracing # echo schedule > set_ftrace_filter
> /debug/tracing # echo function > current_tracer

Sorry no. The correct way you want to do this is:

/debug/tracing # echo > trace
That will reset the buffer for you and give you the desired result.

-- Steve



> /debug/tracing # cat trace
> # tracer: function
> #
> # TASK-PID CPU# TIMESTAMP FUNCTION
> # | | | | |
> <idle>-0 [000] 21.997778: irq_enter <-handle_IRQ
> <idle>-0 [000] 21.997785: idle_cpu <-irq_enter
> <idle>-0 [000] 21.997794: local_bh_disable <-irq_enter
> <idle>-0 [000] 21.997800: tick_check_idle <-irq_enter
> <idle>-0 [000] 21.997807:
> tick_check_oneshot_broadcast <-tick_check_idle
> <idle>-0 [000] 21.997814: _local_bh_enable <-irq_enter
>
> After applying this patch, only filtered functions are traced.
>
> Signed-off-by: Rajesh Bhagat <rajesh.lnx@gmail.com>
> ---
> kernel/trace/trace.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index a3f1bc5..f4fb190 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3058,8 +3058,10 @@ static int tracing_set_tracer(const char *buf)
> ret = -EINVAL;
> goto out;
> }
> - if (t == current_trace)
> + if (t == current_trace) {
> + tracing_reset_online_cpus(tr);
> goto out;
> + }
>
> trace_branch_disable();
> if (current_trace && current_trace->reset)




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