linux-kernel - Re: [PATCH 1/5] perf tools: fix incorrect ordering of callchain entries

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Date:	Fri, 22 Apr 2016 10:55:53 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Chris Phlipot <cphlipot0@...il.com>, acme@...nel.org,
	mingo@...hat.com, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] perf tools: fix incorrect ordering of callchain
 entries

On 19/04/16 11:56, Chris Phlipot wrote:
> The existing implentation implementation of thread__resolve_callchain,

Remove 'implentation'

> under certain circumstanes, can assemble callchain entries in the

'circumstanes' -> 'circumstances'

> incorrect order.
> 
> A the callchain entries are resolved incorrectly for a sample when all
> of the following conditions are met:
> 
> 1. callchain_param.order is set to ORDER_CALLER
> 
> 2. thread__resolve_callchain_sample is able to resolve callchain entries
>    for the sample.
> 
> 3. unwind__get_entries is also able to resolve callchain entries for the
>    sample.
> 
> The fix is accomplished by reversing the order in which
> thread__resolve_callchain_sample and unwind__get_entries are called
> when callchain_param.order is set to ORDER_CALLER.

Can you give an example of the commands you used and what the call chain
looked like before and after.

Also please run ./scripts/checkpatch.pl

> 
> Unwind specific code from thread__resolve_callchain is also moved into a
> new static function to improve readability of the fix.
> 
> Signed-off-by: Chris Phlipot <cphlipot0@...il.com>
> ---
>  tools/perf/util/machine.c | 57 ++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 41 insertions(+), 16 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 0c4dabc..dd086c8 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1806,8 +1806,6 @@ static int thread__resolve_callchain_sample(struct thread *thread,
>  	int skip_idx = -1;
>  	int first_call = 0;
>  
> -	callchain_cursor_reset(cursor);
> -
>  	if (has_branch_callstack(evsel)) {
>  		err = resolve_lbr_callchain_sample(thread, cursor, sample, parent,
>  						   root_al, max_stack);
> @@ -1918,20 +1916,12 @@ static int unwind_entry(struct unwind_entry *entry, void *arg)
>  				       entry->map, entry->sym);
>  }
>  
> -int thread__resolve_callchain(struct thread *thread,
> -			      struct callchain_cursor *cursor,
> -			      struct perf_evsel *evsel,
> -			      struct perf_sample *sample,
> -			      struct symbol **parent,
> -			      struct addr_location *root_al,
> -			      int max_stack)
> -{
> -	int ret = thread__resolve_callchain_sample(thread, cursor, evsel,
> -						   sample, parent,
> -						   root_al, max_stack);
> -	if (ret)
> -		return ret;
> -
> +static int thread__resolve_callchain_unwind(struct thread *thread,
> +                                            struct callchain_cursor *cursor,
> +					    struct perf_evsel *evsel,
> +					    struct perf_sample *sample,
> +					    int max_stack)
> +{
>  	/* Can we do dwarf post unwind? */
>  	if (!((evsel->attr.sample_type & PERF_SAMPLE_REGS_USER) &&
>  	      (evsel->attr.sample_type & PERF_SAMPLE_STACK_USER)))
> @@ -1944,7 +1934,42 @@ int thread__resolve_callchain(struct thread *thread,
>  
>  	return unwind__get_entries(unwind_entry, cursor,
>  				   thread, sample, max_stack);
> +}
> +
> +int thread__resolve_callchain(struct thread *thread,
> +                              struct callchain_cursor *cursor,
> +                              struct perf_evsel *evsel,
> +                              struct perf_sample *sample,
> +                              struct symbol **parent,
> +                              struct addr_location *root_al,
> +                              int max_stack)
> +{
> +	int ret = 0;
> +	callchain_cursor_reset(&callchain_cursor);
> +
> +	if (callchain_param.order == ORDER_CALLEE) {
> +                ret = thread__resolve_callchain_sample(thread, cursor,
> +                                                       evsel, sample,
> +						       parent, root_al,
> +						       max_stack);
> +		if (ret)
> +			return ret;
> +                ret = thread__resolve_callchain_unwind(thread, cursor,
> +                                                       evsel, sample,
> +						       max_stack);
> +	} else {
> +                ret = thread__resolve_callchain_unwind(thread, cursor,
> +                                                       evsel, sample,
> +						       max_stack);
> +		if (ret)
> +			return ret;
> +                ret = thread__resolve_callchain_sample(thread, cursor,
> +                                                       evsel, sample,
> +						       parent, root_al,
> +						       max_stack);
> +	}
>  
> +	return ret;
>  }
>  
>  int machine__for_each_thread(struct machine *machine,
>