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ring-buffer: check for divide by zero in ring-buffer-benchmark

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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>
This commit is contained in:
Steven Rostedt 2009-05-08 11:03:57 -04:00 committed by Steven Rostedt
parent 5a772b2b3c
commit d988ff94c1
1 changed files with 6 additions and 0 deletions
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6
kernel/trace/ring_buffer_benchmark.c
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@ -294,6 +294,12 @@ static void ring_buffer_producer(void)
pr_info("Total iterations per millisec: %ld\n", hit + missed); 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 */ /* Caculate the average time in nanosecs */
avg = NSEC_PER_MSEC / (hit + missed); avg = NSEC_PER_MSEC / (hit + missed);
pr_info("%ld ns per entry\n", avg); pr_info("%ld ns per entry\n", avg);