linux-kernel - Re: [PATCH] of: introduce event tracepoints for dynamic device

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Message-ID: <90e008a7-0660-99b9-edbe-6bf146268ba8@gmail.com>
Date:   Wed, 19 Apr 2017 22:24:58 -0700
From:   Tyrel Datwyler <turtle.in.the.kernel@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Frank Rowand <frowand.list@...il.com>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>, robh+dt@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, nfont@...ux.vnet.ibm.com,
        mingo@...hat.com
Subject: Re: [PATCH] of: introduce event tracepoints for dynamic device_node
 lifecyle

On 04/19/2017 07:33 PM, Steven Rostedt wrote:
> On Wed, 19 Apr 2017 16:27:10 -0700
> Tyrel Datwyler <turtle.in.the.kernel@...il.com> wrote:
> 
>> # echo stacktrace > /sys/kernel/debug/tracing/trace_options
>> # cat trace | grep -A6 "/pci@...000020000018"
> 
> Just to let you know that there is now stacktrace event triggers, where
> you don't need to stacktrace all events, you can pick and choose. And
> even filter the stack trace on specific fields of the event.

This is great, and I did figure that out this afternoon. One thing I was
still trying to determine though was whether its possible to set these
triggers at boot? As far as I could tell I'm still limited to
"trace_options=stacktrace" as a kernel boot parameter to get the stack
for event tracepoints.

-Tyrel

> 
>  # cd /sys/kernel/debug/tracing
>  # echo "stacktrace if common_pid == $$ && reason == 3" \
>    > events/tlb/tlb_flush/trigger
> 
>  # cat trace
>             bash-1103  [003] ...1  1290.100133: tlb_flush: pages:-1 reason:local mm shootdown (3)
>             bash-1103  [003] ...2  1290.100140: <stack trace>
>  => copy_process.part.39
>  => _do_fork
>  => SyS_clone
>  => do_syscall_64
>  => return_from_SYSCALL_64
> 
> -- Steve
>