On 06/05/2014 09:12 AM, Steven Rostedt wrote:
I'm going through some of the warnings that Fengguang Wu's test bot has
discovered, and one of them is from a MIPS allmodconfig build.
https://lists.01.org/pipermail/kbuild-all/2014-May/004751.html
kernel/trace/trace_benchmark.c: In function 'trace_do_benchmark':
kernel/trace/trace_benchmark.c:84:3: warning: comparison of distinct pointer types lacks a cast [enabled by default]
kernel/trace/trace_benchmark.c:85:3: warning: comparison of distinct pointer types lacks a cast [enabled by default]
kernel/trace/trace_benchmark.c:38:6: warning: unused variable 'seedsq' [-Wunused-variable]
vim +84 kernel/trace/trace_benchmark.c
78 if (bm_cnt > 1) {
79 /*
80 * Apply Welford's method to calculate standard deviation:
81 * s^2 = 1 / (n * (n-1)) * (n * \Sum (x_i)^2 - (\Sum x_i)^2)
82 */
83 stddev = (u64)bm_cnt * bm_totalsq - bm_total * bm_total;
> 84 do_div(stddev, bm_cnt);
> 85 do_div(stddev, bm_cnt - 1);
86 } else
87 stddev = 0;
88
Is there something special with do_div in mips that I should be aware
of?
Yes. MIPS is using the implementation in asm-generic/div64.h, which
per the comments in that file has a useless pointer compare to find just
this type of issue.
Ralf: As a side note, while looking at arch/mips/include/asm/div64.h, I
saw that the implementation of __div64_32 in that file will be unused,
and is also completely broken due to the first parameter never being used.
David Daney
