On Thu, 05 Jun 2014 10:12:16 -0700 David Daney <ddaney.cavm@xxxxxxxxx> wrote: > 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. You mean this comment? /* The unnecessary pointer compare is there * to check for type safety (n must be 64bit) */ But stddev is s64. Ah, but the compare is: (void)(((typeof((n)) *)0) == ((uint64_t *)0)); so it's complaining about a signed verses unsigned compare, not length. I think I can ignore this warning then. Thoughts? -- Steve > > > 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 >
