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

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Date:	Sat,  8 Aug 2009 04:26:35 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>
Subject: [PATCH 1/3] perfcounter: Initialize tracepoint record before any use

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>
---
 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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