linux-kernel - Re: [PATCH 1/3] perfcounter: Initialize tracepoint record before any use

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Date:	Sat, 8 Aug 2009 04:30:39 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 1/3] perfcounter: Initialize tracepoint record before
	any use

On Sat, Aug 08, 2009 at 04:26:35AM +0200, Frederic Weisbecker wrote:
> Despite that the tracepoint record is always present when the
> PERF_SAMPLE_TP_RECORD flag is set, gcc whines, thinking it might not
> be initialized:
> 
> kernel/perf_counter.c: In function ‘perf_counter_output’:
> kernel/perf_counter.c:2650: warning: ‘tp’ may be used uninitialized in this function
> 
> Then, initialize it to NULL and always check if it's not NULL before
> dereference it.
> 
> Reported-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Mike Galbraith <efault@....de>
> Cc: Paul Mackerras <paulus@...ba.org>
> ---


Hmm, sorry I've resent the perf tools series by mistake. Please
ignore the [PATCH */4] "perf tools: *" series that has already been
sent.

The only ones are [PATCH */3] perfcounter: *

Thanks.


>  kernel/perf_counter.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
> index 142ae5a..a6963e2 100644
> --- a/kernel/perf_counter.c
> +++ b/kernel/perf_counter.c
> @@ -2647,7 +2647,7 @@ void perf_counter_output(struct perf_counter *counter, int nmi,
>  		u64 counter;
>  	} group_entry;
>  	struct perf_callchain_entry *callchain = NULL;
> -	struct perf_tracepoint_record *tp;
> +	struct perf_tracepoint_record *tp = NULL;
>  	int callchain_size = 0;
>  	u64 time;
>  	struct {
> @@ -2718,7 +2718,8 @@ void perf_counter_output(struct perf_counter *counter, int nmi,
>  
>  	if (sample_type & PERF_SAMPLE_TP_RECORD) {
>  		tp = data->private;
> -		header.size += tp->size;
> +		if (tp)
> +			header.size += tp->size;
>  	}
>  
>  	ret = perf_output_begin(&handle, counter, header.size, nmi, 1);
> @@ -2784,7 +2785,7 @@ void perf_counter_output(struct perf_counter *counter, int nmi,
>  		}
>  	}
>  
> -	if (sample_type & PERF_SAMPLE_TP_RECORD)
> +	if ((sample_type & PERF_SAMPLE_TP_RECORD) && tp)
>  		perf_output_copy(&handle, tp->record, tp->size);
>  
>  	perf_output_end(&handle);
> -- 
> 1.6.2.3
> 

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