From: Steven Rostedt Date: Fri, 8 May 2009 15:03:57 +0000 (-0400) Subject: ring-buffer: check for divide by zero in ring-buffer-benchmark X-Git-Tag: v2.6.31-rc1~401^2~48 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d988ff94c1074c4c914235c8591bcceafb585ecf;p=karo-tx-linux.git ring-buffer: check for divide by zero in ring-buffer-benchmark 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 Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c index 7d3aef93c49f..8d68e149a8b3 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);