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Date: Wed, 26 Sep 2018 15:16:05 +0530
From: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To: Joel Fernandes <joel@...lfernandes.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Laura Abbott <labbott@...hat.com>,
Kees Cook <keescook@...omium.org>,
Anton Vorontsov <anton@...msg.org>,
Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
Colin Cross <ccross@...roid.com>,
Jason Baron <jbaron@...mai.com>,
Tony Luck <tony.luck@...el.com>, Arnd Bergmann <arnd@...db.de>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Joe Perches <joe@...ches.com>,
Jim Cromie <jim.cromie@...il.com>,
Rajendra Nayak <rnayak@...eaurora.org>,
Vivek Gautam <vivek.gautam@...eaurora.org>,
Sibi Sankar <sibis@...eaurora.org>,
linux-arm-kernel@...ts.infradead.org,
LKML <linux-kernel@...r.kernel.org>,
linux-arm-msm@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...nel.org>,
Tom Zanussi <tom.zanussi@...ux.intel.com>,
Prasad Sodagudi <psodagud@...eaurora.org>,
tsoni@...eaurora.org, Bryan Huntsman <bryanh@...eaurora.org>,
Tingwei Zhang <tingwei@...eaurora.org>
Subject: Re: [PATCH 3/6] tracing: Add tp_pstore cmdline to have tracepoints go
to pstore
On 9/26/2018 2:55 AM, Joel Fernandes wrote:
> On Sat, Sep 8, 2018 at 1:28 PM Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>>
>> Add the kernel command line tp_pstore option that will have
>> tracepoints go to persistent ram buffer as well as to the
>> trace buffer for further debugging. This is similar to tp_printk
>> cmdline option of ftrace.
>>
>> Pstore support for event tracing is already added and we enable
>> logging to pstore only if cmdline is specified.
>>
>> Passing "tp_pstore" will activate logging to pstore. To turn it
>> off, the sysctl /proc/sys/kernel/tracepoint_pstore can have '0'
>> echoed into it. Note, this only works if the cmdline option is
>> used. Echoing 1 into the sysctl file without the cmdline option
>> will have no affect.
>>
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> ---
>> .../admin-guide/kernel-parameters.txt | 21 ++++++++
>> include/linux/ftrace.h | 6 ++-
>> kernel/sysctl.c | 7 +++
>> kernel/trace/Kconfig | 22 +++++++-
>> kernel/trace/trace.c | 51 +++++++++++++++++++
>> kernel/trace/trace.h | 7 +++
>> 6 files changed, 112 insertions(+), 2 deletions(-)
>>
> [...]
>> config GCOV_PROFILE_FTRACE
>> bool "Enable GCOV profiling on ftrace subsystem"
>> depends on GCOV_KERNEL
>> @@ -789,4 +810,3 @@ config GCOV_PROFILE_FTRACE
>> endif # FTRACE
>>
>> endif # TRACING_SUPPORT
>> -
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index bf6f1d70484d..018cbbefb769 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -73,6 +73,11 @@ struct trace_iterator *tracepoint_print_iter;
>> int tracepoint_printk;
>> static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key);
>>
>> +/* Pipe tracepoints to pstore */
>> +struct trace_iterator *tracepoint_pstore_iter;
>> +int tracepoint_pstore;
>> +static DEFINE_STATIC_KEY_FALSE(tracepoint_pstore_key);
>> +
>> /* For tracers that don't implement custom flags */
>> static struct tracer_opt dummy_tracer_opt[] = {
>> { }
>> @@ -238,6 +243,14 @@ static int __init set_tracepoint_printk(char *str)
>> }
>> __setup("tp_printk", set_tracepoint_printk);
>>
>> +static int __init set_tracepoint_pstore(char *str)
>> +{
>> + if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0))
>> + tracepoint_pstore = 1;
>> + return 1;
>> +}
>> +__setup("tp_pstore", set_tracepoint_pstore);
>> +
>> unsigned long long ns2usecs(u64 nsec)
>> {
>> nsec += 500;
>> @@ -2376,11 +2389,45 @@ int tracepoint_printk_sysctl(struct ctl_table *table, int write,
>> return ret;
>> }
>>
>> +static DEFINE_MUTEX(tracepoint_pstore_mutex);
>> +
>> +int tracepoint_pstore_sysctl(struct ctl_table *table, int write,
>> + void __user *buffer, size_t *lenp,
>> + loff_t *ppos)
>> +{
>> + int save_tracepoint_pstore;
>> + int ret;
>> +
>> + mutex_lock(&tracepoint_pstore_mutex);
>> + save_tracepoint_pstore = tracepoint_pstore;
>> +
>> + ret = proc_dointvec(table, write, buffer, lenp, ppos);
>> +
>> + if (!tracepoint_pstore_iter)
>> + tracepoint_pstore = 0;
>> +
>> + if (save_tracepoint_pstore == tracepoint_pstore)
>> + goto out;
>> +
>> + if (tracepoint_pstore)
>> + static_key_enable(&tracepoint_pstore_key.key);
>> + else
>> + static_key_disable(&tracepoint_pstore_key.key);
>> +
>> + out:
>> + mutex_unlock(&tracepoint_pstore_mutex);
>> +
>> + return ret;
>> +}
>> +
>> void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
>> {
>> if (static_key_false(&tracepoint_printk_key.key))
>> output_printk(fbuffer);
>>
>> + if (static_key_false(&tracepoint_pstore_key.key))
>> + pstore_event_call(fbuffer);
>
> Can you not find a way to pass the size of the even record here, to
> pstore? Then you can directly allocate and store the binary record in
> pstore itself instead of rendering and storing the text in pstore
> which will be more space (and I think time) efficient. I also think if
> you do this, then you will not need to use the spinlock in the pstore
> (which AIUI is preventing the warning you're seeing in the
> event_call->event.funcs->trace() call).
>
Right, I can check this out.
Thanks,
Sai
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