Messages in this thread Patch in this message | | | Date | Fri, 08 May 2009 12:20:35 -0400 | From | Steven Rostedt <> | Subject | [PATCH 2/2] ring-buffer: check for divide by zero in ring-buffer-benchmark |
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From: Steven Rostedt <srostedt@redhat.com>
Although we check if "missed" is not zero, we divide by hit + missed, and the addition can possible overflow and become a divide by zero.
This patch checks for this case, and will report it when it happens then modify "hit" to make the calculation be non zero.
[ Impact: prevent possible divide by zero in ring-buffer-benchmark ]
Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- kernel/trace/ring_buffer_benchmark.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c index 7d3aef9..8d68e14 100644 --- a/kernel/trace/ring_buffer_benchmark.c +++ b/kernel/trace/ring_buffer_benchmark.c @@ -294,6 +294,12 @@ static void ring_buffer_producer(void) pr_info("Total iterations per millisec: %ld\n", hit + missed); + /* it is possible that hit + missed will overflow and be zero */ + if (!(hit + missed)) { + pr_info("hit + missed overflowed and totalled zero!\n"); + hit--; /* make it non zero */ + } + /* Caculate the average time in nanosecs */ avg = NSEC_PER_MSEC / (hit + missed); pr_info("%ld ns per entry\n", avg); -- 1.6.2.4 --
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